I have (all sold ) stripped M16 upper recently removed from department rifles for conversions. These uppers do not have any stampings denoting which forge - the rifles were early Colt M16's.
There is a 4 digit ID stamped on the rear of the handle. There are mostly handling marks and some finish wear inside and around some of the ejection ports.
These are small pin uppers and with a little refinishing and $20 in parts you have yourself a nice Air Force upper for your rifle. $45 each shipped insured. Money order or PayPal transfer is fine.
Thanks for looking.