Seiko 7A38 - by the numbers



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Getting back to case-back gaskets, and what I wrote on the previous page - here's a copy and paste:


There are two part numbers called up in the 7Axx bills of material / parts lists: FH3180B0A and FH3181B01. ‘FH’ stands for Flat Hard (rubber), and ‘318’ is the inside diameter. They are of slightly different section, in that the ‘0B0A has a slightly larger outside diameter (to match the width of the case-back flange), and also appears to be marginally thinner. As a general rule (and again something of an over-simplification), the ‘0B0A is used on Sports 100 models with a ‘Double Wave’ case-back and the ‘1B01 is used on watches with plain case-backs. There are odd exceptions to this rule, such as the 7A38-6080’s and -6090s, which are designated SQ100, but have plain case-backs, and hence used the ‘0B0A gasket to help achieve their 10 Bar WR rating.

I use new OEM Seiko gaskets on watches I intend to wear regularly, as proper sealing of the case-back joint is critical to prevent moisture ingress (from perspiration). But I have used various other substitute replacement gaskets in the past, including Labanda’s (Australia) p/n FE318BA12 (the same original Seiko p/n was used on the 6M15, 6M25 and H201) and Cousins’ cheaper flat round rubber gaskets, which are made in softer rubber – with some success. Both when re-using old gaskets (which I sometimes do, on watches destined only to sit in one of my various collection boxes), or when fitting a new gasket, I always give both gasket and the case-back threads a light smear of Seiko Silicone grease.

My earlier use of Labanda's substitute part number FE318BA12 stemmed from a very old thread on the old Network54 SCWF:

I just happened to look again at their website this evening and noticed this:

Not only that, but on the previous page they are also listing substitute pusher seals:

January 18, 2013 at 5:34 PM Flag Quote & Reply

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An enterprising Thai eBay seller 'Seikoforever' who already appears to do a roaring trade selling over-priced generic replacement 7Axx crystals (to the uninitiated) has added a new listing for a 7A28 / 7A38 DIY gasket kit:

Now I have no idea what gaskets are actually used in a 4006 'Bellmatic' (and care even less), but Seiko 7Axx's use flat ring case-back gaskets. Not only that, but there are two types of case-back gasket and pusher seals used, dependent on the model. Caveat Emptor.

February 3, 2013 at 4:49 AM Flag Quote & Reply

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Just over a week ago, I put together a small bulk order for the two types of case-back gaskets and pusher seals used in Seiko 7Axx's.

What I was ordering for myself (alone) would have covered Labanda's minimum order value of $25, but Simon doubled up my order.

Then Arpad (who I'd been exchanging PM's with about 'alternative' case-back gaskets recently) tacked on one pack of each as well.

Postman delivered today. Initial reactions (without examining them with a loupe) is that all looks good. Lot cheaper than Cousins too.

February 13, 2013 at 6:09 AM Flag Quote & Reply

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For anybody who might be thinking to themselves ....

Why didn't he order enough for everbody (the selfish b*st*rd) or much bigger quanties so he could sell them single gasket at a time to forum members (at cost) ? :/ Or even on eBay for a fat profit. :) You know what the answer is going to be .... and it ain't polite. :P

This was very much a 'toe in the water exercise'. ;)

Back in the dim and distant dark days of March 2009, when I was still a 7A38 'Newbie', I wanted some case-back gaskets.

That was when I bought those which I mentioned in my first post on this page:

But I have used various other substitute replacement gaskets in the past, including Labanda’s (Australia) p/n FE318BA12.

I actually bought one pack of 5 case-back gaskets for $2.50Au - and then got charged $14 postage for sending them to the UK !! :o

Labanda's website (now) is very much like Cousins UK. Indeed they stock all kinds of other watchmaker's tools, movements, parts, etc.

They too will deal with any individual direct, just like Cousins (there's the usual check the tick-box 'wholesale only' disclaimer thing).

Problem is the postage costs, which is why rather than just order what I needed, I asked Simon and Arpad if they were interested.

Here's what I ended up ordering for the three of us (Simon and I both doubled up on the case-back gaskets):

Total cost $81Au. The (international) shipping which gets added on later, once you've submitted your order was $20Au. Total $101Au.

Seemed like a reasonable size order. Goods value needs to be over $25Au anyway, because once you start shopping, you'll see this:

Problem is that $25Au (currently equivalent to £16.66) is just over the VAT chargeable limit for merchandise (£15) by HM Customs. :mad:

February 13, 2013 at 5:01 PM Flag Quote & Reply

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I'm pleased to say that our little 'toe in the water' joint exercise has subsequently proved rather fortuitous.

I followed it up with a cheeky 'post-mortem' email to Luke of the Labanda sales team in Brisbane. As a direct result ....

To assist international buyers (read those poor victims susceptible to unreasonable VAT / Customs clearance charges),

.... Labanda Pty. will be dropping their minimum order value to $10Au:D

What a result eh ? So now you know where to get your gaskets from. ;)

February 15, 2013 at 5:21 AM Flag Quote & Reply

Posts: 202

Just a quick update about these Labanda gaskets.

I tried the EC0060B0A pusher gaskets today not on 7A28, neither on a 7A38 but on a H558-5009 aka Arnie. Luckily they have the same pusher gaskets as the 7Axx Sports 100 have.

Here are some pictures before the surgery:

As you can see the original gaskets were absolutely worn, it was really necessary to replace them.

Unfortunately I was lazy (and also forgot) to take photos about the process. It's a pain in the ass job. I managed to tear/rip the first gasket. The problem was that I didn't apply any silicone grease either on the gasket or the pin.

On the next turn I was much wiser! I applied a good amount of grease on both and the gasket slipped easily onto the pin.Then I did the same with the second pusher...went easily again. (Thanks for God there are only two pushers on H558 :D )

I used a fine tweezer and a small needle plus the Seiko silicone grease of course.

I'm very satisfied with the result, the gaskets were fitted perfectly on the pin and the whole pin assembly went inside the case flawlessly.

What else I could does worth to buy it! :)

February 20, 2013 at 8:30 PM Flag Quote & Reply

Posts: 41

I've got a couple of bits of info to drop off after some recent watch tinkering...

1. If you're ordering case back gaskets from Cousins then the ISO Swiss ones are worth the extra. The rubber is harder and they hold a circular shape better, unlike the floppy Cousins ones that aren't even round to start with :/

2. Although I splashed out on a genuine 310W64GN00 crystal for my 7A28-7040 I wanted to help finding an alternative, so in my last Cousins order I threw in a Sternkreuz MFH310.  There are some decent bevels on the packet diagram but in reality there's almost no visible bevel on either side!  You have to look really close to see a tiny bevel on one side but basically it's square.

Aftermarket crystals "are like a box of chocolates, you never know what you 'gun get"  :|  So we can cross that one off the list, has anyone tried a XMF 310.848 yet?

August 26, 2013 at 12:22 PM Flag Quote & Reply

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With any of Sternkreuz's XMF 'Special Forms' crystals, unless the original Seiko part number is cross-referenced in their catalogue, as it is, say with the XMF300.860 (Seiko p/n 300W08GN00) and XMF320.927 (Seiko p/n 300W42GN00), where you know what the Seiko crystal looks like, I'd say any of those with bevelled edges are something of a 'blindfolded chocolate box dip'. Yes their XMF310.848 may have a Seiko cross-reference p/n of 310W17GN00, but do a reverse look-up on Seiko Oz, and it comes up with 'No data found'.

Didn't you notice what I wrote in reply to Arpad on the previous page ? (my posted dated May 16th 2012).

If you don't want to pay the price for a genuine 310W64GN00, you could (but I wouldn't) try XMF 310.847 (2.2mm) or 310.848 (1.9mm), but like the 310.853, from the silhouette sections shown in the Sternkeuz catalogue illustrations they both would also appear to have a disproportionately large polished bevelled edge.

August 26, 2013 at 12:56 PM Flag Quote & Reply

Posts: 41

Yes I saw the discussion on the previous page before deciding to just buy the pricey original while it's still available.... Buying three (possibly ill-fitting) Sternkreuz alternatives would probably have cost the same in the end.  But I was happy to drop a couple of quid on the non-Special Forms MFH just in case it was a cheap alternative.

Judging by the crystals I've bought so far, catalogue/packet illustrations are virtually meaningless and bear no relation to what you get.  How hard would it be to give a spec of depth/angle/polish?  I guess they don't consider these cases where there's a tight overlapping bezel to contend with :/

The 7A28-7040 is pretty common so Sternkreuz should really be doing something suitable... I'll hit them with an email to that effect and see what they say.  They might have considered it previously and baulked at the unusally steep bevel on it, perhaps not worth tooling up for.

August 26, 2013 at 3:40 PM Flag Quote & Reply

Posts: 41

I got a reply from Sternkreuz on why they don't do a 310W64GN00 equivalent, seeing as it's for one of the more common 7A28's:

"es gibt leider keine ausreichend große Nachfrage nach diesen Gläsern, daher haben wir sie nicht in unser Lieferprogramm aufgenommen"

Translated: "Unfortunately, there is not sufficient demand for these glasses, so we have not included in our product range" 

Oh well maybe they're right, I've only seen ones with battered bezels rather than chipped/scratched crystals (mine only has a couple of small scratches that bother me, being a perfectionist).  At least we might be getting decent aftermarket bezel rings, they're more important to face-lifting a watch than finding a cheap crystal :)

August 27, 2013 at 12:10 PM Flag Quote & Reply

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Lawrence. Why would they have been seeing any demand - while stocks of the original 310W64GN00 crystal are still available ? :/

August 27, 2013 at 12:37 PM Flag Quote & Reply

Posts: 41

Does anyone other than Cousins still have them now though?  Let alone cheaper than £13 + postage!  Perhaps the last time they looked Seiko had stock so no harm asking them to consider it.

To be fair the 7A scene is pretty small and hardly a huge money-spinner, even with the number you buy and restore ;)

August 28, 2013 at 8:27 AM Flag Quote & Reply

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New forum member Tim (MTX371) recently asked a question about recommended substitute crystals in the Installing Crystal thread ....

Right at the bottom of Page 1. Ideally I'd like to keep all the part number related information together in this thread, but it's done now.

One other additional question Tim asked me, by PM - not in that thread, was what replacement crystal to use on a 7A38-6090.

Our messages read:


Got a (7A38-)6090 today... Which crystal can you recommend for this beauty? MDM 275 domed?


Hmm. That's an interesting question, Tim. :/ 

In the past, I'd always got them from Cousins - either as Seiko p/n 275W30HK01 or Sternkreuz XMF275.701. 

But now it looks like they (Cousins) have discontinued them as well.

Maybe you want to try ordering that one from a German watch material house - ?

Because if you check the Sternkreuz catalogue it is still currently listed.

I'm at work at the moment, so I can't check, but a MDM won't be right. From memory the original crystal is domed / flat bottomed. 

So really you'd need to be looking at something like Cousins p/n DF150CMH275 (if you can't source the Sternkeuz XMF275.701).

See: (halfway down page 7). 

There Sternkreuz give the dimensions for their XMF275.701 as: 27.5mm diameter / overall height 2.4mm and edge thickmess / 1.3mm.

Here's the domed crystal options available from Cousins:

January 9, 2014 at 6:22 AM Flag Quote & Reply

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Excuse the slight  ramble, but I'd thought about this again this morning, for a different reason - but it is connected. :P

I'm working on a 5J22-0A60 Kinetic at present, for a chap at work - replacing a badly scratched crystal and the inevitable capacitor.

The original crystal, Seiko p/n 280P30JZ0B is 28mm diameter, domed, flat bottomed and approx. 2.6mm thick at the edge.

It's still available - but unfortunately it's a 'special' (with a superfluous chrome bubble) and costs £21.50 + VAT from Cousins !! 

So I looked for a cheaper substitute and found Cousins own branded 28mm x 2.5mm domed crystal p/n DF250CMH28 - at £1.50. :)

Before the package from Cousins arrived, I was a bit concerned it might be more domed than the original Seiko - it isn't - if less so.

I fitted it this morning and it works a treat. 8)

I just dug out one of the badly scratched Seiko p/n 275W30HK01 crystals I'd removed from 7A38-6090's in the past and measured it.

The dimensions are slightly different to what Sternkreuz quote for XMF275.701 - 2.5mm overall height and 1.6mm deep at the edge.

Ergo, if the proportions of Cousins 1.5mm thick flat-bottomed domed crystals are the same as their 2.5mm thick, I've just bought ....

Then for a 7A38-6090 crystal replacement, I reckon a p/n DF150CMH275 is now probably the best (and cheapest) way to go. ;)

January 9, 2014 at 7:06 AM Flag Quote & Reply

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I've written something up about these Cousins cheap alternative domed flat bottomed crystals in the 7A38-6060 / -6070 model thread this afternoon, where I've successfully used a Cousins' p/n DF3MMCMH300 in place of the original (obsolete) Seiko p/n 300WF2FK01 crystal in my 'beater' 7A38-6060, but it won't hurt to mention it here as well. :P Here's a partial copy and paste of what I wrote there:

I still haven't identified a proper 'correct' substitute for obsolete Seiko p/n 300WF2FK01 crystal. But I have found something that works.

What I'd failed to mention in my description of the original crystal is that it was also 'double domed' - i.e. convex on top and concave on the underside. Nobody makes an off-the-shelf double-domed crystal 3.5mm thick ! A couple of weeks ago, I was looking for a cheap substitute crystal for a work colleague's Seiko Kinetic I was fettling. Cousins actually had the original Seiko crystal in stock, but it was £21.50 + VAT ! :o That's when I discovered Cousins (own brand) domed flat bottom range.

It was the 3.0mm thick at bottom left which caught my eye. :)


Seeing as they only cost £1.50 +VAT (compared to 'unobtanium') thought it might be worth a shot. So I ordered a p/n DF3MMCMH300.

Another point worth mentioning is that unlike many Seiko 'Diver's there is no need to remove the bezel on the 7A38-6060 to press out the crystal. There is no bevelled edge. You can do it with bezel in situ. Here's a side on view showing the slight difference in thickness:

There were also two things I omitted to mention there ....

Firstly that in using a domed flat bottomed crystal in place of a double-domed original crystal, there is some slight distortion when you look at the watch side on. But I'm talking about an almost horizontal angle, where you wouldn't normally be able to see the hands. ;)

Secondly is that I've sussed another alternative ! 8)

February 1, 2014 at 12:06 PM Flag Quote & Reply

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Having been the European HQ 'spare parts guy' for a major multinational corporation (intel), in a former life, a part of my career that I look back on both fondly and proudly - then not been able to solve this 'little' parts problem had understandably frustrated the hell out of me for nearly 5 years ! :mad:

I make no secret of the fact that my favourite 'Seiko 7A38' is actually the Yema Spationaute III Aragatz. 

This watch (or should I clarify by saying the larger 43mm version) and its stablemate the Yema N8 Flygraf use a pretty unique crystal.

It measures 30.5mm Ø by 2.8mm thick and is double-domed. The doming is quite shallow. The overall maximum height is 3.8mm.

I first needed a replacement crystal as far back as December 2009, when I bought this beater / parts watch - my first Spationaute III:

I used that watch as a basis to build my much-loved 'Mission Flags' bitza.

There was no hope of re-using the original crystal though - it was totally beyond redemption. But I never did throw it away either.

I had a pretty good idea that the Yema crystal was a Seiko part, but I've never been able to cross-reference it. I did buy a couple of Seiko 305Wxxxxxx part number crystals 'on spec', but neither proved close enough. Initially I plumped for a Sternkreuz p/n MDH305.

All three of them were too thin - in fact only 2.0mm thick, compared to the 2.8mm original Yema crystal, but the Seiko crystals also had polished bevel edges and lead-in bevels to boot, which effectively ruled them out. The two Seiko crystals are used in the H558-5010 and H558-5020 'Fieldmaster' (or some suchlike), so if anyone happens to be looking for one of these crystals give me a shout. ;)

I got round the (lack of) thickness of the Sternkeuz MDH305 by using it in conjunction with a Sternkreuz 'L' section crystal gasket, but I was never entirely happy with it, because it was more pronouncedly domed, which you can gauge from the relection in this old photo.

Since then I've wasted an incredible amount of time on this 'parts problem'. I've talked to 4 different companies in the UK and France about the possibility of grinding me a suitably accurate replacement crystal (using my old beaten-up Yema crystal as a pattern). I even got a quote from G-S Supplies in Rochester, New York (a.k.a. Germanow-Simon Machine Co.) - the same people who manufacture Jonathan Koch's various Seiko repro' crystals for him. Initially, over the phone, they quoted $25 each. I was trying to find their email again, but IIRC, they wanted something like $250 to produce 5 (their minimum order quantity) 'one-off prototype watch glasses'. :o

The guy in France - a genuine Paris-based watchmaker seemed keen, but when he insisted I had to send him the watch as well as the old crystal, I didn't bother responding. If you ever find yourself in a similar position, may I save you some time by recommending that you don't waste ANY talking to these people: - they proved a complete and utter waste of time ! :roll:

Oh Yes, then there was this not quite so badly scratched crystal that came out of another Yema Spationaute III, that I tried polishing:

Maybe I'm too much of a perfectionist, but after literally hours of sweat and toil, I still hadn't achieved the final result I'd hoped for. :(

February 1, 2014 at 1:10 PM Flag Quote & Reply

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So, to cut a long story short, when I placed my last order with Cousins UK, not only did I order one of their p/n DF3MMCMH300 to try in my 'beater' 7A38-6060, I gambled by also ordering a 30.5mm Ø x 2.5mm thick domed flat bottom crystal - their p/n DF250CMH305. :)

Here it is with the original badly graunched and scratched crystal saved from that Yema Spationaute III parts watch of 5 years ago.

Not easy to capture in a photo, but the amount of doming is almost identical. Who cares about the 0.3mm difference in thickness. :D

Guess what I'll be fitting in my other Yema Spationaute III resto' project tomorrow ? Not the original Yema crystal I'd been polishing ! 

February 1, 2014 at 3:34 PM Flag Quote & Reply

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One final word from the wise - if you should decide to 'experiment' with any of these domed crystals yourself.

From my recent experience of them, I've found that the Cousins 'Domed with a Flat Bottom' crystal range are very shallow domed to a very similar upper profile as the OEM Seiko crystals you might be hoping to use them as a substitute for - if not sightly less than them.

As I mentioned above, the Sternkreuz MDH range (and presumably this applies to other thicknesses) are more pronouncedly domed.

What I'd forgotten completely - and it wasn't till I came to put those other 'unwanted' double-domed crystals away, that I was reminded by a solitary packet left in the bottom of the box, was at the same time as I ordered my first Sternkreuz p/n MDH305, to use in my Yema Spationaute III 'bitza', back in December 2009, I'd also ordered one of the (much) cheaper Cousins equivalent double-domed crystals - their p/n D200CMH300. All I will say, is that unless you want your watch to end up looking like a 'Bubble Boy', don't even think about going there ! Completely the opposite of their flat-bottomed domed crystals, these crystals are horrendously domed in comparison !

February 1, 2014 at 5:16 PM Flag Quote & Reply

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Originally posted by Rob Benham on February 11, 2014 at 4:39 PM (in the eBay section).

This made me look twice.  I even had an exchange of PMs with him.  Waste of time.

February 12, 2014 at 6:30 AM Flag Quote & Reply

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I'm not sure quite what your issue is Rob. :/ Is it with the eBay seller or the crystals he is offering ? Price perhaps ? :|

This is the same Thai eBay seller Seikoforever I cited at the top of this page - offering incorrect section case-back gaskets.

He clearly doesn't give a fig about accurate appearing / fitting substitute replacement parts.

But then many of his buyers don't appear to be that fussy either. :roll:

As far as I can remember all Seiko 7A38's using a 31.0mm Ø x 1.5mm thick crystal are plain without a polished polished bevel edge.

But the one he's offering has (according to this photo embedded in his description):

They may be worth trying in certain sizes - e.g. 30.0mm and 32.0mm Ø x 1.5mm to see how they compare with the Sternkreuz XMF's.

Me ? Nah - certainly won't be. 

I've recently sussed out another Thai supplier: KHH Watch:

February 12, 2014 at 6:49 AM Flag Quote & Reply

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