In case anyone is interested, I am resisting the temptation to add another project to the list.....    http://www.gunbroker.com/Auction/ViewItem.aspx?Item=493309485   seller says GM or H&R, probably rebuild.  Price seems in line with current market.  I spent a bunch of time looking at the GM/H&R sticky and this does not appear to be a GM receiver. (can't see any of the forging flaws talked about in the sticky)  H&R?  Any experts want to clarify what they believe this to actually be.

He mentions it not having flash on the front of the handle. My H&R does have it.

Is that right, A1/603 uppers without Colt proof marks are most likely H&R or GM made? I have a couple and wasn't sure of their origin.

That looks like a GM upper receiver from what he has pictured.  If you contact him, ask for pictures of the front of the carry handle and the back side of the forward assist.  All the GM uppers I have seen have what looks like sanding marks that run from side to side where the forging flash was removed, and it looks like the original forward assists had a number cast in a depressed circle.  Also, the style of the "3" looks the same as most of the GM upper receivers I have seen.  Ask for full size pictures of all the ones he has.  It looks like there is a little texture in it, all of the GM receivers I have seen have been pretty smooth.  There is a chance it is original finish.

Hot link for you phone guys here

GM or H&R for sure. My upper on my XM16E1 is the same thing and it is a GM.

Could be either GM or H&R. Hard to tell without original barrel. Definitely looks like the grainy black arsenal paint finish.

Lack of specific forging flaws doesn't necessarily mean it isn't GM, as they used forgings from more than the one die.

Nice upper tho, would be a great start for either a GM or H&R build. Fair price these days too.

I didn't know that the GM & H&R Upper Receivers had the Rebated Front Lug.  Learn something new..