Apc who


I have 3 references for the headstamp APC they are from older pulications
1 = Austin Cartridge Co. USA
2 = Clinton Cartridge Co. USA [manufactured in Germany ] on a old rimfire ID chart origin long forgotten
3 = Sears Roebuck USA [manufactured in Germany ] Headstamps by Warren Horne
Can anyone clear the confusion or was there a German manufacturer or exporter in the 1800’s using A P C .