OK. So I have temporarilary gone brain dead. Can't recall what the markings on the upper receivers mean. I'm talking about the symbols like the "key hole" or "little pyramid looking thing". Whats the deal again? I know some receivers don't have any markings at all.

US forged marking

forgot what company--i think it was ceirro or something

top quality

They are the forging marks to indentify the company who did the forging.

I remember they were forge markings but can someone tell me which markings go with what company? I know there are two or three. The most common seem to be the key hole and the little pyramid thing.

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

Circle/Crooshairs w/"AR" = ArmaLite

CM = Colt / Martin Marietta

D (stylized) = Diemaco

DK = Diemaco / Kaiser Aluminum

E = Emco

F keyhole = FNMI / Cerro Forge

FA = FNMI / Anchor Harvey

FK = FNMI / Kaiser Aluminum

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