Adam Dodds might know. he used to work at Davidson's and knew Sowerby's in the late 50's and 60's!
I have just bought a pristine 1948 book on Pressed Glass by Davidson, privately printed by them to celebrate 3 generations of Davidsons, and it is not there.
Looks like a tooth pickholder to me but very late Victorian early Edwardian, turn of the century!