That is a McM Hunter style stock, probably the original Sako Hunter style, worth at least $500 at today's prices. If I was in the market for that rifle, even if I was only buying it to rebarrel it, I think that $599 makes it a very good value.
I have the same stock on my matched pair of Husqvarna 8000s in 256 Newton and 338-06, plus a dozen or more McM Hunter style stocks on Remington, Ruger, and Weatherby rifles.
I have several Husqvarnas with mannlicher style stocks and 20.75" barrels. The muzzle blast is there, but not noticeable in the field when you're concentrating on put lead on target within the next couple of seconds.
