I have an old Okeefe and Merritt range, model # A 3848, Ser # 206012.
The oven control knob became very hard to turn, and finally fell off. There were some teeny little metal parts, some of which seemed home made, that fell out and that I suspect were the remains of some sort of clip, as I cannot figure out how to get it to stay on and function. It is a Robertshaw valve. I think this shows the valve, it is a type C and I think the demolished clip goes where the "OFF" is shown.