Forging marks/makers.
A (splintered): Anchor Harvey Aluminum
AF: Alcoa Forge
C AF: Colt Alco Forge
C MB: Colt / Mueller Brass
Cardinal (stylized): Cardinal Forge
CH: Colt Harvey Aluminum
CK: Colt / Kaiser Aluminum
Circle/Crooshairs w/"AR": ArmaLite
CM: Colt / Martin Marietta
D (stylized): Diemaco
DK: Diemaco / Kaiser Aluminum
E: Emco
EK: EMCO/Kaiser
E MB: EMCO/Mueller Brass
F keyhole: FNMI / Cerro Forge
FA: FNMI / Anchor Harvey
FK: FNMI / Kaiser Aluminum
FM: FN/Martin Marietta
FMB: FNMI / Mueller Brass
Keyhole: Cerro Forge
L: Lewis Machine & Tool
LK: LAR / Kaiser Aluminum
LM: LAR / Martin Marietta
M (under diamond): Mueller Industries
PA: Capco / Anchor Harvey
PM: Capco / Martin Marietta
Square: Brass Aluminum