sorry to hear about his loss
Not a Constellation Im afraid, looks like a manual movement of some type. If it was an automatic it would be written on the dial.
I cant help with case ref but it looks to me like a late 50s or 60s watch. If you can get any info from any service documents case ref, movement number this would help you alot with a like for like replacement.
Some of the more experienced members will probably be able to give you alot more info , but there were a lot of these made with various calibers over the decades and it wont be easy to give exact details
Have you got any more pics ?