Forge Markings used on AR15's and M16's:

Forge Markings used on AR15's and M16's

Offset Square is: Brass Aluminum Forging
LMT is: No Forge Marks, but marked LMT or L is: LMT
AF is: Alcoa Forge
C AF is: Colt Alco Forge
A (splintered) = Anchor Harvey Aluminum
C MB is: Colt / Mueller Brass
Cardinal’s head (stylized bird head) is: Cardinal Forge
CH is: Colt Harvey Aluminum
Crosshairs w/"AR" is: ArmaLite
CK is: Colt / Kaiser Aluminum
CM is: Colt / Martin Marietta
D (stylized) is: Diemaco
DK is: Diemaco / Kaiser Aluminum
E is: Emco
EK is: EMCO/Kaiser
E MB is: EMCO/Mueller Brass
FA is: FNMI / Anchor Harvey
FK is: FNMI / Kaiser Aluminum
FM is: FN/Martin Marietta
FMB is: FNMI / Mueller Brass
LK is: LAR / Kaiser Aluminum
LM is: LAR / Martin Marietta
M "diamond" is: Mueller Industries
PA is: Capco / Anchor Harvey
PM is: Capco / Martin Marietta
Square (symbol) is: Brass Aluminum
M-16 markings:
CAF Colt / Alcoa Forge
CH Colt / Harvey Aluminum (1st Colt Forgings)
CM Colt / Martin Marietta
DK Diemaco / Kaiser
FK, FS, BK, DK, EK, FK, AF, CW, AA, FS Bushmaster
LK FN / Kaiser
LM LAR / Martin Marietta (Army Spares Contract)
“Splintered A” F: FNMI Anchor Harvey“Splintered A” F: FNMI Anchor Harvey
“Splintered A” C: Colt Anchor Harvey
"Splintered A" Olympic Arms? (Anchor Harvey)

Verified upper receiver forge markings used by AR-15 upper manufacturers/sellers

DSA - Cardinal forge
Rock River - Cardinal forge
Delton - Cerro forge, square
DPMS - Cerro
Spikes Tactical - Cerro
Stag - Cardinal, Cerro
LWRC- splintered A
Para USA - ZM
Knight’s Armament - Cerro (keyhole)
Wilson Combat - splintered A
Double Star - Cerro
Smith &Wesson - Cerro
Daniel Defense - Cerro
Sabre Defense - Cerro?
Remington - Cerro
BCM - Cerro, square
Bushmaster - Cerro
Stag - splintered A, Cardinal
J&T Distributing (Doublestar) - Cerro, C
CMMG - Cerro
Colt M4 - Cerro (C keyhole), square, Cardinal (“C“ bird‘s head), C AF