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I dunno what they're worth now, but that looks just like the one I had for my Hbar in the late 80's and I think they were ~$250 then. I might even have the receipt kicking around in a file somewhere, just as a reminder to kick myself repeatedly for selling my AR and all its accessories.
Edit: If that is an M261 conversion they were $299 in 1989 from Milarm.
I am pretty sure it wont work with the Colt 22 bolt.
I have used it in a Colt Ar 15 and a C7. at 25 yards groups were dime-sized. Real good for practicing shooting sitting and standing, which was what i ahd to work on.