The Omega Crystal That Did Not Fit

I had a first time experience this evening and as I could not find anything similar on this and other forums I thought I share it with you and hopefully can get some good advice as well. I would also like to point out I am pure hobbyist, so I may have overlooked something obvious, so any well thought advice are always welcome.

For the past week I have been restoring an Omega Seamaster Ref 2766 with a cal 344 movement. The movement is now ticking along fine on my workbench and before casing up the watch I wanted to replaced the generic crystal with a proper Omega Crystal. According to the documentation I have access to the correct crystal for this movement shall be a 063PX5000, and if anyone has any other information please let me know.

So when I am aligning the crystal before using the press the crystal is just dropping into place without any force, and also equally easy comes out of the case. I am quite surprised as it usually demands some force to get it into place and commonly you are rewarded with a plop as well when it settles. After checking I have taken the correct crystal I start to take some measurements and find that the case is same size or larger than the crystal. Measuring with a caliper I get:

Crystal bottom part: 29.57-29.60 mm
Case inside diam: 29.60-29.63 mm

I would not take the absolute measurements as values but considering the crystal shall have an OD of 29.62 mm they are in the correct range. I also tried with a second crystal just to ensure that there was not anything wrong with the first one but same loose fit and same measurements.

I have also double checked that case is correct and it is not a recase or any other switchout. I also looked for signs of polishing or machining inside the case but could not find any. So I would be interested to hear if this is maybe common with vintage Seamasters, that there are some wear in the case where the crystal shall be seated, and I have maybe just been fortunate to not encounter it before.

My second query is what would be a proper way to fix this. Using glue and adhesive feels like a sort of last solution and also not being reversible. On other hand I could just use a generic crystal of the proper size or there are maybe some other smart fix to this.

Happy to hear from you.

Thanks in advance
Robert

As I cannot buy directly from Omega it has been bought on internet but in an Omega Sealed Package. If I remember rightly it came in a lot with other sparesparts from a watchmaker that closed his business.

I did not keep the package of the first crystal I tried with but attached is a picture of package for the second crystal I tried. It is not exactly the same as it has the steel ring but measurements I have assumed shall be the same.

That may be the case.

Thank you for the replies and advice.

The dimensions are awfully similar to C-Case aftermarket crystals, being 29.6mm - and their distinction is being loose fits, however since the original crystal was a loose fit too, I guess this isn't the case

Also I believe there's some variance for original crystals as well

Does this case have a corresponding bezel?

What Archer said.
This is the "166.010" case and case back I got taken on, with my actual 166.010. When I ordered the etched Omega crystal, it was wayyyy too big. I was NOT happy.

166.010 bezel diam = 34.7
?(Geneve)? bezel diam = 33.5

Yes it does.