hi,
Few weeks ago i bought on ebay 1973(?) longines.
6922
17 jewels
serial no. 52117648 (end of 1973...?)

My watchmaker replaced crystal, polished case, replaced strap with gold plated buckle and did a proper service. Dial has missing [O] letter, index at 6 and 30" mark on sub-sec, but i like it being old - not going to renovate dial.
I have however problem with case back - was missing from the beginning and i am trying to find replacement. For time being watchmaker was able to find crystal to secure movement (movement look really cool), but want to make the project completed.

Can you help and advice what case back i should look for, please?

Regards,
Piotr