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At this point it would probably just be better to go with celluloid but would it work if you epoxied two pieces together so that it was thick enough?

On the site it says .035”-.045”, so it's on the thinner side but if it's rigid enough(and not too rigid) I think it could work. I've never handled tortoise but aren't most ivory scales in that...

Tor-Tis

I guess celluloid is already tried and tested but this material seems interesting to me.
It sounds like it would be very easy to make a pair of good looking scales out of this, just warm...