I looked up a photo of a 1865 Spencer hammer. I misunderstood the description, when asked. The hammer on my gun is flat in the right side. No bevel. Just a worn area on the striking surface that I misunderstood from your comment, Rim fire.
Serial numbers match.
Six groove rifling / 22” barrel.
The rounded appearance to the top of the receiver is likely due to wearing out many wire wheels to remove the rust, years ago. An unintentional outcome.
This carbine looks to be all 1860 original, EXCEPT the ‘65 ladder site.
Got a few original parts and screws from S&S (Thanks JSpencerman)
So all working and sharp now. The new stocks are some labor. It’ll be awhile before they’re fitted and finished.
Thanks for all the info gents!
(Photos posted by Two Flints)