Nice gun, and thanks for posting it!
I'd think it a Berks gun more than upper Susquehanna, as Spotz suggests. And it doesn't really have much to suggest a specific maker.
Personally, I'd call it a buck and ball as opposed to a smooth rifle or fowler, but that's just me. I have a gun with a part octagon/ part round barrel with front and rear sight, with straight rifling. You might look deep into the barrel for any signs of rifling.
As for the Rev War connection; not likely, as the gun isn't that old. It could have been around for the War of 1812 though.
It looks like your family is taking good care of it, so keep doing whatever you've been doing!
John