Well now, since you have the box and all the goodies that came with it and if it is in excellent condition I would up that value to $700 to $750.
I bought a 6" LNIB (the guy said it had never been shot) for $575 but that was a couple of years ago. Prices have gone up since then. I've seen some very nice 6" K22s in the box recently marked $750 at local shows but the same guys have had them for a little while.
I don't look at gunbroker too much and prefer to keep a watch on what I see sell locally. There are some deep pocket guys on gunbroker.
Prices are all over the place these days. At the last show I went to a guy had a M63 marked $1250, with no box or anything.
Maybe I need to start collecting knives again.