Found at a yard sale this morning.
It was with some other reloading stuff, but may not be reloading stuff.
Each is 3 inches long.
They have a stylized ROC and what appears to be a sizing numeric label on one end and a 0.440"x 1.2 deep hole on the other end.
Each cylinder is stepped half way end to end. 1.5" of small and 1.5" of larger.
As labeled ......... measured diameters
4 1/2-5 1/2 ...... .600 and .630"
6 1/2-7 1/2 ...... .663 and .697"
8 1/2-9 1/2 ...... .729 and .760"
10 1/2-11 1/2 ... .793 and .825"
12 1/2-13 1/2 ... .857 and .888"
These measurements may be a tiny bit off as my calipers seem to have a glitch in the needle drive gear.
These parts are made from aluminum and mounted on a cheesy plastic block with pins.
The shoulder, or step, is very sharp.
Definitely not a commercial application in my mind.
The 6-7 one is the only one showing any signs of use, with some faint lengthwise scratching on the smaller diameter, like a go-nogo.