You have what's called a long lever tear drop (LLTD) ratchet. I call it the "baby rattle" style, because the selector knob sort of reminds me of a baby's toy. If I recall correctly, they were made by EASCO from 1967? to about 1992, being replaced by the figure-8 plate style of ratchet.
Yours is probably toward the earlier end of that time frame.
Solid user, rebuild kits are still around, on ebay if nothing else. Keep it!