Not an easy thing to cope with I am sure. The gun is most likely, as Dr. Drew stated, a Crescent Arms .410 quail gun- parts? Hard to say. The Ithaca black buttplate looks like a replacement, also note the wood screw at the top (heel) is a straight shank, whereas the wood screw at the bottom (toe) is a Phillips head--
I love history, trivia and playing amateur detective- I helped a widow find various barrels etc. for her late husband's collection of Savage 99 lever rifles- he was also a hunting companion and had two LC Smiths, both field grades, a 20 and a 12- knowing a bit about your uncle's occupation and work habits might be a clue in the search for the missing parts.
Back when I was heavy into split cane fly rods, a good friend who was a residential township building inspector found several rod cases in older homes, stuffed in the bracing of the floor joists in the basement- most of the rods I bought that way were Montagues and South Bends (trading stock) but one was a Heddon 35 in near Mint shape- and the quest goes on.
Having the parts made you need to make this .410 double functional again would be cost prohibitive, as I am sure you realize. If older guns could indeed talk, what fascinating stories they would tell.