Seiko vintage 6139-7100 crystal removal / replacement.

[Endeavor]

Hello All;

today I received a 1970's 6139-7100 "helmet" Seiko. The case and the original bracelet were, for a nearly 50 years old watch, "as new".

Never worked on these types of Seikos before, I've been watching YT video's hoping to learn how to remove the crystal. I think that I get the drift, but to be sure, I like to ask the forum.

 

It seems that by certain Seiko models one has to first remove the bezel. This 7100 case seems to be one of them, since it has a slot for a case-knife.

Am I correct it that?

Then what next? Can I expect some rings, and after that push the crystal out of a rubber seal?

Even thought the flat crystal looks great, certainly for its age (and perhaps I may use it again), but out of curiosity, can the crystal be replaced with a flat "standard" sapphire crystal?

Hope to hear from our Seiko specialists.......

Oh, BTW, from the serial number on the back 728957, is this a 1977?

[ManSkirtBrew]

2 hours ago, Endeavor said:

Oh, BTW, from the serial number on the back 728957, is this a 1977?

Seiko codes and part number decoder.

[xyzzy]

Since 1978, Seiko has put an alphanumeric code on the back that tells you how to take the case part.  Which your watch doesn't have, being from 1977.

But there is a document Seiko used to publish with a table, and a scanned copy exists, and 6139-710 is in it (the last digit isn't used).  So you're lucky.  This case has class type F4:

 

You are supposed to remove the bezel. The edge of the bezel extends over the glass.  The crystal has a large bevel on the top that allows this.  Because of that, it's likely a standard flat replacement glass will not fit.

Seiko 3. Casing Guide.pdf

[Endeavor]

27 minutes ago, xyzzy said:

So you're lucky. 

Indeed, thanks for the document and your help