Back in the 40s (I think) my father saw Johnny Weissmuller at the NY Athletic Club swim across the pool with a glass of water on his back and not spill a drop!

I don't think many folks can do that now a days!!

Waybe

I think you have to swim nude on camera to get to carry one, anyhow. Maybe even the water glass trick.

Looks as if ivory is best repro of the genuine rubber version. The woodwork stacking might be an easier way to make up a mold for a fiberglas and resin cast which would be more durable than ivory, and closer to the original in being fake ivory.