Need help identifying an AR/M16 upper (PIC HEAVY)

I'm trying to find out some information on it and all I can come up with is CK = Colt / Kaiser Aluminum.

I'd like to find out approximately what year it was manufactured, if it is indeed a Colt, what model it came on, and an estimated value. Any help would be greatly appreciated.

I didn't see ANY markings on the barrel when the handguards were removed either, but again any help would be appreciated.

Just going through Wikipedia I was thinking it could be a Commando but still not sure, can't believe everything you read on Wiki anyway. Looking for an expert that can give me a definitive answer or at least point me in the direction of someone who can..

Sights = A1
Forward Assist = Yes
Case Deflector = No
Barrel Length = 11.5"
Barrel profile = (I assume it's an A1)
Barrel twist = (not sure)
Handguards = Short ribbed
Bayonet Lug = No
Muzzle Device = A1

http://en.wikipedia.org/wiki/AR-15_variants

Colt # 639
Model XM177E2

Colt # 733
Model M16A2 Commando

Colt # 733A
Model M16A2 Commando

Colt # 735
Model M16A2 Commando

SARDUY, I think I'd be more inclined to go with the XM177E2 since it has the 11.5" barrel, not the 10"

As far as I can tell from the info I've managed to gather it is a 639 XM177E2. Or a Commando 733, 733A, 734, 734A or 735. I'll have to look at the twist rate as that seems to be the only difference between the XM177E2 and the Commandos since the XM177E2 did NOT have a case deflector but it was an option on the commando.

Thank you everyone for your help, it is greatly appreaciated.