I have purchased a nice used AR15 with a Bushmaster lower and shopbuilt upper.  I would like to know the manufacturer of the  A2 upper reciever but it has no markings except two small stampings on the ejection side ( right) and between the port and barrel nut/delta ring.  They are a small triangle with a P in it and and small square with a C in it.   The barrel is an Olympic and the bolt unit is supposed to be Colt.  Thats another question, Are colt parts identifiable?  This bolt unit is an odd greenish color.  Any help or ideas would be appreciated.   SimSon

Sounds like your upper has Colt proof marks on it. A Colt bolt carrier will be marked with the letter C on the left (non ejection port) side about 2" or so back from the front (bolt end). A Colt bolt will have the letters MPC marked on it's side. Usually takes good light to see it though.

Larry

Here's one of my gray Colt's proofmarks.  Sounds just like what you are describing:


I'm under the impression that they are only stamped on uppers that go out on complete rifles, as opposed to the replacement uppers "kits".   Hope this helps.

Your photo and stamping are a good match to my upper reciever.  Thanks much for the info and good photo.  I'm satisfied that my upper is a colt. The seller told me that the upper was "used Colt  parts"  although they sure weren't used much.  For some reason the upper was sold as parts. It's great information and knowledgeable guys like you that prompted me to sign on to this forum.  STRENGTH AND KNOWLEDGE IN NUMBERS.  

Thanks, the last person I tried to help called me a moron...

www.ar15.com/forums/topic.html?b=3&f=12&t=198589

Quoted: Here's one of my gray Colt's proofmarks.  Sounds just like what you are describing: www.boomspeed.com/kisara/proofmarks.jpg I'm under the impression that they are only stamped on uppers that go out on complete rifles, as opposed to the replacement uppers "kits".   Hope this helps.

Think you may br wrong about the marks not being on kits; if the "kit" in fact was a complete barrelled upper with bolt/carrier assembly.  It would have been test fired after assembly, before shipment, and that's when the stampings are put on.  Bare replacement uppers wouldn't have the marks, and I seem to recall a couple of A2 uppers Colt apparently shipped to  the military to upgrade A1s to the adj. rear sight, that I didn't notice the marks being on.

In any event, you are NOT an moron; and I don't care what anyone else has to say about it