What a super neat rifle, especially with it being a family rifle! You seem to have some question as to its make. It appears to be a Cleveland Hoffman and I'm not a real expert but I'd say the engraving is Kornbrath. The carving is very Cleveland Hoffmanish as is the barrel with that gorgeous 1/4 rib! Plus, Hoffman was known for using commercial Mausers. It should be marked as a Hoffman or a Griffin&Howe in either case. However, if your Uncle was so tied in to the era's custom gunmakers to get them to do piece work for him, it could have a mottled pedigree (and that's in no way meant to be dispargaing!! Hell, I wish I just knew someone who knew Adolph or any of those guys, much less have a family member who ran with them!). With it being a carbine set up for a Lyman 48, it makes you wonder if he mounted the scope later on and if so, did he have it rebored??
This is one of those rifles I'd just love to coon finger!!!