This is a brand new set of 2 thumb lock nuts for the ribbon to work on Corona 3 folding typewriters. Without it, the ribbon reverse will not work properly, the spool nut is installed on top of the ribbon to hold it down and rotate it.
This screw is made of high-quality, stainless steel. It is essential for a properly working Corona 3 typewriter.
It will fit all of the following models:
Corona 3 Folding