Geologists call them concretions and and megaspherulites.
described how the ball was rolled against the blockage and let loose to “passe avec violence” against the obstruction.
There are a few exceptions where not even mainstream researchers can deny that they are made.
Such as the ones in Costa Rica, that you see in the following two images: Approximately 300 of these have been counted in Costa Rica.
In the USA no such version was offered, though it was possible to fit the ordinary machine with a conversion kit - a bed-mounted 6-station capstan unit and a cut-ff (forming) slide.
Even in pre-WW2 years Atlas had made novel use of new materials and all models had their changewheels, most other gears, handwheels, pulleys, clasp nuts and other small items made from "ZAMAK".