I'm no expert either but I know that to a Militaria collector it would be worth less than one in original condition, however it would appeal to a collector of trench art making it a cross collectible, should get you $60-$90 I would think.
That's my guesstimate and i'm sticking to it.
UNIQUE WW2 CATTARAUGUS 225Q FIGHTING KNIFE TRENCH ART ALTERED STAG HANDLE
(don't know if it will all fit, may have to use ebay subtitle for .50 if selling there)