I'm not sure about what are their good prices are but I've seen them around for $1200 to $1400.
I used to own the same Colt R6551 which I bought in 1991, blue label box, they usually have an A2 flash suppressor, mine did not have a pinned sear block which in my own opinion a more desirable version, some later versions had sear blocks.
There are also some of them without flash suppressors which comply with the '94 AWB law, the only way to find out what year it was made is to have your friend call Colt, they will say when it was actually made.
The 6551 were made from '91 to '94 and was replaced by the Match Target series models to comply with the AWB.
For me personally if I ever get one of those rifles again I would not part it out, in my opinion they're worth more in the original factory condition because they only made them for a short period of time.