An acquaintance and I were discussing AR stuff when the topic turned to old type ARs eventually turning to Colt SP1s. Most of you know that the SP1 was a sporter/civilian model. It had A1 sights, slabsided upper (no forward assist or shell deflector). So he says, "hey, I have an stripped SP1 upper receiver, do you want it?" "What do you mean want?" I ask. "You can have it, no charge. I have no use for it and am never going to build a rifle with it." says he. So he brings it out, I look it over and see that it has never been used as in, never been made into a rifle. No marks, no scratches, no wear, nothing. It has the rear sight but no dust cover ever installed. That is unusual as I don't think Colt sold stripped uppers. Long story short I took it home and compared it to my SP1 upper... But guess what? They are not the same. Can you tell the difference? (not counting the ejection port cover or color) How bout now?