I got this at the gunshow for $30. it was spray painted black, I sprayed some Simply Green on it, the paint started to flake off.
Moly Koted, this will make a nice .22LR upper.
[img]http://wsphotofews.excite.com/028/bJ/SS/cG/GS76193.jpg[/img]
[img]http://wsphotofews.excite.com/035/bO/l4/vw/GG83075.jpg[/img]
It looks like hell, but it fits good on my lower.

Derek45,

I'm pretty certain, but I could be wrong, the "C" inside the square signifies it as a Colt product.

If the front pivot is the same size as the rear, then it is an original M16. Not M16a1, as that had a forward assist behind the ejection port.

If the front pivot is a larger hole, then you have a Colt SP1 upper receiver. This is the original commercial AR15 unit.

Good find. I'd have paid $30 for it in a minute.

The front hole is the Military size, not the SP-1 size. It fits up well with my Bushmaster lowers.
I guess it's an early M16 or USAF upper.
Who knows where this thing has been.
I'm glad I found it.