The roller on the tool pictured above has a flat surface around its circumference. Founded in the late 1930's, the Sivon Manufacturing Company still exists as "Specialists to the Rubber Industry" but now out of Perry, Ohio. I emailed the above pictures to them, asking if they could identify the tool. Here is the response I received:
"Hello. I have been told it was for tire build-up. Probabaly (sic) made for BF Goodrich. Of course it is no longer made by us-or wonder if it is even used. We manufacture equipment for the rubber industry now.They did that in the 40's also."
I don't know what "tire build-up" is and unfortunately the company representative didn't respond to my follow-up request for further clarification. So, I don't know if this tool was actually used to mold tires, or was somehow used when fitting tires to rims.