Hi Yannis
The case pdf available from Cousins in the UK lists this expansion ring as 07905500E. They do not show it as available.
If it is of any use, I have a selection of expansion rings from 565 movements which should give you the internal diameter, case clamp cut-outs etc. I have no idea which model this one came from.
View attachment 70645
Now as the Omega Speedmaster was worn on the moon and this is an Omega expansion ring it must have some historical significance. Note it has not even been cleaned thus retaining It's patina. I feel sure that I could place this on ebay with a starting bid of $500 and be overwhelmed with interest.
Alternatively, as you are a member of this forum, I could let you have this for a 'one off special price' of the postage to your address plus (optionally) the price of a beer.
Let me know if it is of any use.
Chris
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