About four years old, good condition, A2 profile, 1/7 twist, chrome lined, A2 handle.  Barrel stamped "C MP 1/7 5.56 NATO", upper stamped "CM" near rear sight, front sight tower "C" at top, a bell stamped on the bottom.

Also, a used TA01 (non-NSN) ACOG mated to the upper, so likely of the same approximate vintage.  The reticle still glows red, no scratches on the lenses or anything in the field of view.  Rubber armor is moderately abraded and scratched-- it was not babied.

The seller said "make me an offer" and I don't know where to start.  Thanks for your help.

The upper if it has the bolt should be worth $300.00 no idea on the sight try EE .Good luck

if there is a low round count on the barrel, maybe 500 or less, i'd offer 400 with bolt/carrier/charging handle. it is a desirable twist rate and barrel contour.

ACOG, i'd offer 425.

The upper is complete with B/BC/CH, but I don't know what markings to check for on them to verify they are Colt as well.  This upper would qualify as "good".  Plenty of handling wear, but little mechanical wear.  Bore is clean, brass deflector is clean.  No holes in the finish.

BUSTER51: I did try to find similar prices on the EE, but most of the items there are new or NIB.  
I also checked if I should post a price check *in* the EE, but didn't see anything in the rules.  I searched the board for "price check" and found most of them in General Ar-15 discussion.  Maybe I should have broken this up into two posts, one into Optics and one into Uppers?

2minkey: Yes, the twist caught my eye.  The stamping was very faint.

If I've seen a price on a NIB Ta01, how would I figure the value of a four-year old one?  If the Tritium should be replaced in 12 years, then it's 1/3 through it's service life.