if you manage a full genealogy - think about a piece in the Parker Pages

From the locations of the serial number that you have told us and shown us, the gun is most certainly serial no. 147

Logan, I would tend to believe it is chambered for the 12-b brass shell, I own ser# 97 and 029 both are back action guns and are chambered 12-B, Try to find a 12-b shell and see how it fits, Gary

I'll try to locate a 12-B to check the chamber size - thanks for the suggestion.

I'd like to clean the gun up a bit - is there anything I should know about cleaning a gun of this age? Is it safe/wise to use modern solvents and oils?

You would do well to send it to a reputable gunsmith. I have used Brian Dudley who is on this forum and there are others on here as well.