I know that this may be a bit trivial, but I have 2 Colt uppers and want to know which is considered the lesser desirable in today's market. I will choose it for a Cerakote job.
I have one that is "C" marked with Keyhole and one that is Cage Coded with Square. Which would you paint?
Also as a data point, I recently purchased a Colt M5 CQC upper (complete). There are no markings on the upper at all, other than a Keyhole forge mark. No "C", no Cage Code.