Well, I've turned down $1.2k for mine.

FWIW, Colt developed the 7" DOE 9mm upper for the Department of Energy as a cab gun for couriers driving tractor-trailers carrying nuclear materiel. They tried the 10.5" 9mm upper but felt it was still too long for the circumstances.

The DOE contract was for 800 complete guns, so Colt bought enough barrels/handguards/front-sights for 2,000, hoping more contracts would come in. But none did, and in the '90s, in one of their then-common periodic "make up some stuff to sell and stave off bankruptcy" drives, assembled the 1,200 remaining uppers and sold 'em off cheap to distributors. Almost all of these lacked the front sling swivel, because when they put them together, Colt inventory happened to be out of those. They showed up at gun shows at the time and sold in the $750-$850 range and quickly disappeared.

In the last few years, many folks have been making exact clones of the parts, so those are out there. I have no idea of the current value, but I expect it would cost $500-600 to build a perfect non-Colt clone.

Today, if you can find an original Colt unfired, still NIB upper (without sling swivel), you can probably get close to $2k for it at auction. An actual-but-fired-with-swivel upper from an actual DOE gun might be worth more, or less, to a collector, but would be a pretty cool item.

For those who do not know what we are talking about: Mine, on my Colt M16A1 lower with 20-round Colt mag (though it's much cooler with a 100-round Betamag drum):

Bill, you still have first refusal if I can ever bring myself to part with it.

RenegadeX, I just checked gunbroker.com. There is one original DOE upper on there with a $2.5k Buy It Now price and a clone with a starting price of $895. So if you ever decide to part with it, you'll do well. Of all the 9mm uppers, you are getting the most valuable variation.