24 Vintage Black Glass Knuckle Bone Buttons 1.2cm Buttons.

Smooth black glass, moulded into an unusual shape
- looks like knuckle bones to me.
I expect it was done this way to add depth and interest as they catch the
light on the surfaces.
Their display card suggests 1930s/40s.
They are 1.2cm wide and have an integral glass shank on the back.
I just have 2 sheets of 24 and 2 lots of 6.