Hi Steve,
Since no one has tossed out anything on your 175, I'll stick in a blurb. It sounds like you may have an aftermarket custom, with that stone work.
I thought all the 175 and the smaller 170 were all aluminum handles. At least all of mine are. Since they aren't hugely popular or collectable, I have bought mintys of both the 170 and 175 in the $10 to $25 range.
I think they are sleepers among Buck knives with the one handed opening, and smoothness of an Alpha folder. I most always carry a little red/black marble 170 in a pocket for when I don't want to unclip the 179 out of a back pocket if around a lot of people..