Omega Dynamic auto/date movement retention

[RoyC]

I have one of the above - a 1967/8 model and off hand I can't recall the cal. Someone else serviced it for me (a friend who has done lots of work on higher value/complex movements for me). After using it for a while - timing's very good - the split stem suddenly popped out. The movement had rotated slightly and I had to take it out end push the inner stem back into the setting position before re-casing the movement and refitting the outer stem. Everything was fine and I wore the watch on and off for a week or so, letting it run down and resetting occasionally. All good. Next time I picked it up to reset  it the stem fell out again and I can clearly see that the movement is slightly rotated. I bought a new stem with my next order from the cousins. However I don't think that wear is the problem. The original is mighty tight to refit. I think the problem is that the movement, er, moves and the stem parts slip apart horizontally (or nearly so.)

I don't want to pester my friend about this. We do barter deals and he's got a lot on his plate right now. So, can someone tell me how the movement is secured? I realise that it rotates clockwise from the 11.00 position to secure in position  but I also recall that it didn't feel like a very positive location. I could substitute the new outer stem temporarily as an experiment but I'm pretty sure this isn't the problem.

As an aside, split stems along with spring loaded detents are two pet hates.

Any relevant advice would be appreciated.

Roy

[watchweasol]

Hi The movements are usually secured in to the case using locking pieces or screws,  were these replaced when last serviced. If you can provide the calibre number we may be able to find a tech sheet for the watch.

[RoyC]

I've asked. It came originally from SE Asia and anything is possible. Cosmetically good though. I've just opened it up -again - and it's a cal. 565. It doesn't do my nerves any good handling it because that unobtainable sweep second hand won't tolerate a single refit...

[watchweasol]

Hi  I have attached the tech sheet for the omega 565, you will probably find what you are looking for on it  good luck,  cheers

377_Omega 565 NewLR.pdf

[rodabod]

There are different cases for these front-loading types, but it’s worth mentioning that some use plain, flat movement retaining tabs which are simply screwed into the movement to provide a key into the case. 
 

Also, do you have an original Omega tension ring crystal fitted?

[RoyC]

I've asked. It came originally from SE Asia and anything is possible. Cosmetically good though. I've just opened it up -again - and it's a cal. 565. It doesn't do my nerves any good handling it because that unobtainable sweep second hand won't tolerate a single refit...

[RoyC]

It has the original crystal but the fit, while firm, is not what you would call tight.

 

[rodabod]

3 hours ago, RoyC said:

It has the original crystal but the fit, while firm, is not what you would call tight.

 

That doesn’t sound right to me as it should be very tight. From memory, they aren’t just a plain ATC - they have a ridge around the edge which secures them at the correct depth. The tension ring is sized to secure the edge of the dial, at least on the Cosmic version anyway. 
 

Did you confirm that the two movement securing tabs are present or not?