The mark appears to to show a raised ‘A.’ It’s not particularly clear, or pronounced and the base is somewhat concave.
Is this a manufacturing anomaly; or a manufacturers headstamp?
If it is a headstamp; could it be:
(i) Winchester Repeating Arms Co.
(ii) Federal Cartridge Corporation, Minneapolis; possibly in conjunction with American Cartridge Company, Kansas City, MO.
Are these tooling marks?
Any thoughts would be appreciated.