U.S. Arms Co. was a tradename for Crescent guns used by Supplee Hdw., Philadelphia and likely others.
This is a catalog page from 1902

[Linked Image from photos.smugmug.com]

There is a guide to estimated DOM here
https://docs.google.com/document/d/1OxZo5Tkvx2G8eYf747QR9B5RJdN6Siu5JGIhfguSXXQ/edit?tab=t.0

Crescent parts also appear on ebay.

As a piece of family history the gun is of course invaluable, but any gunsmithing costs will far exceed its practical value, and it is unlikely to be safe to shoot. You might consider removing the firing pins, cleaning up the external surfaces, and hanging it in a place of honor in your home.

https://sites.google.com/a/damascusknowledge.com/www/home