My great grandmother's sachets with screw in backs

Anyone know how old or exactly what these are???
These tiny sachets (?) where always in my great grandmother's linen drawer as I remember them from the 50s. My grandmother received them from her, then to my mother, then me.
They appear to be carved from bone and the back handles screw in after a perfume is placed in the hollowed out center. Measurements:
the longer of the two - 1.9cm X 3.3cm
the shorter -1.7cm X 2.8cm

If anyone knows their history or any information I would appreciate knowing.