Old 45-70 Headstamp question

[Lethal Farce]

I have a couple of old Lead round nose 45-70 cartridges. They are silverish (look like steel) in color but not magnetic. The headstamp has an "F" a "3" and a "93" spaced at 120 degrees to each other. Any idea as to the details of what these are?
Thanks, LF

 

[Old Dragoon]

Sounds like a Federal shell to me.