one of my GE-6s has one. they are also called skeleton switches sometimes i think. pretty sure they are only found on very early pedals. like 77-79 type thing
We had a project long time ago where we tried to figure out when the clear switch and momentary LED disappeared. I think we eventually found that the clear switch was replced by the black switch at serial 8300-8500 and the momentary LED disappeared at 9000-9100.