Double O-Ring case

[LittleWatchShop]

Has anyone seen this and know the purpose of two o-rings?

Unfortunately, I did not take a picture showing the outer o-ring, but you can see where it goes.

[AndyGSi]

I'd presume it would be to just get a more secure seal.

[LittleWatchShop]

21 minutes ago, AndyGSi said:

I'd presume it would be to just get a more secure seal.

That was my first guess, but there is the stem passing through the second barrier.  I did not investigate to see if there were some sort of oring there.

I am fixing this for a friend.  He noticed the watch was running slow, so he opened it up to "fix" it.  When he put the back on, the inner oring twisted and got in the way of the autowind weight.  I had to replace both orings.

[HectorLooi]

I think the oring is to press the movement ring down firmly to prevent any wiggle room. A wave washer might do a better job than the oring as the rubber will eventually deform.