I bought two of these pistols. I paid $25 for one and $10 for another. Both had been wallhangers and never fired. One had been on full cock for over 25 years. The metal parts inside the locks had never been hardened and the springs were toast. I had a bunch of spare Siler parts from other locks. So to fix the locks I removed all the original stuff and scrapped it. Fortunately, the Siler Cock fit into the hole in the lock plate well enough. I drilled and tapped new holes in the plate so the Siler parts would work. They both eventually became something that would shoot. Accuracy was not part of the deal though. The best load that I found that worked was buckshot. At 12 feet I could mark up a target board sometimes.
I sold one to a "Pyrate" reenactor (Ahrrrr). Can't remember what happened to the other.
They were something interesting to play with. I get the connection with the Uncle and the desire to fix them up to honor his memory. Just know that these pistols are barely worth the effort to repair outside of the sentiments.