@C W Burfle, It appears they go together like this (excuse my poor computer drawing skills):
The cup is somewhat reminiscent of this type of Lego piece except it has 2 outside diameters (not 3) and the inside hole matches the taper of the nubs on the drum (not a cylinder in shape):
I guess it is possible that both tits broke off so very perfectly, but I feel I have a better chance at the lottery...
Yes, I am aware it is possible to get a 259E-1 drums, but I'm very curious about this setup.