Caseback help

So I have recently been gifted a constellation by my father…..his father brought it over to Canada for him in 1971 (approx.) and the serial number and reference are consistent.

Over the years this was the watch that I associated with him until he retired and the watch went into “storage” in the late 90s.

Here’s the watch.


Here’s the problem….


He has no idea when the caseback medallion went missing but I would like to “make it whole” again if possible. The ask from me is for suggestions. I have a WTB posted for a caseback with no responses. I suspect that the 18k Shackman caseback has been alchemically transformed to unobtainium.

Can I find a caseback as below and and do a transplant? Any other ideas? TIA

Ah, I've just replied to your PM, hadn't seen this post before. Basically, this is the wrong medallion (2852; also, the condition is meh), I think you'll need one like this:



And, unlike with the 2852s etc, the steel examples of your watch come with a steel medallion, unfortunately...

It would be a very helpful info which other watches share the same medallion. Solid gold 2852s have the brick-observatory, too, but I there are different nuances to them:

(Picture taken by @X350 XJR , hope you don't mind me using it)