Colt never really marked the carry handles in any special way.
To make things even more complicated Colt outsourced the production to many, different suppliers over the years.
Some of them were making really crappy products, some of them not. There are many, different carry handles out there that were taken away from the Colt rifles and carbines, but there is no way to confirm that. Here are some of the markings appearing on the Colt carry handles, but there are far more out there - some of them not marked at all...
A (splintered) and some variations of the letter A with some numbers and letter B = 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
Hope this helps. That's what I was able to find over the last 24 hrs.