In the old times Celluloid was the best material on the planet for handles - so many colors, pictures, candy stripes, you name it - it was possible.
In use from twenties to late 60's and manufactured by hundreds, there is really no resale value on most such knives.
If the knife is in perfect shape the value is about $20-$40, but it is a ticking bomb. The scales are already at the point of crumbling off like dry toast.
With the scales already cracked or missing, such knives are good only for parts, or total re-make project. Garage sale value - not more then $5.
Celluloid has a life span of about 50 years before it desintegrates. Also when it does start deteriorating / decomposing so to speak,
it does release chemicals that interact with brass frame/liner turning it green or blue, weakening it so much that it develops cracks, as the chemicals eat through.
I have repaired - restored few fish knives made by Ka-Bar, and some other copies that had sentimental value.
This is very expensive undertaking in labour, materials and shop resources, if the frame is eaten through or significantly weakened - at about $350 per restoration.