Welding Tips and Tricks

I have several old transformer style welders. One is an old P&H Chemetron ac/dc 300 HF. It has a spot for a “electronic timed weld unit” according to the label on the machine face. Am I correct in assuming this would be a primitive pulse unit? Is anybody familiar with the old Chemetron welders. I did a fair amount of google searching, I’ve only found dead ends.

Probably more like a spot weld timer, contactor unit.