45-70 Questions

Started on the 45-70 project and I could sure use some expert help. Can someone assist with the meaning of the ‘600’ on the bullet please
45-70%20GOVT%20-9 45-70%20GOVT%20-9%20FULL 45-70%20GOVT%20-9a%20FULL

Who manufactured this?
45-70%20GOVT%20-12 45-70%20GOVT%20-12%20FULL


The upper case looks to be by U.S.C.Co. but the stamp? No idea, sorry.

The lower looks to be U.M.C.Co., but I could well be wrong.

Catalog number from a former collector?