I think this machine uses a pedal similar to the ones on the Dialarc and Marshall Dynabolt. They are a big lump with a rheostat inside, nothing like a modern pedal with a little potentiometer.
If it It Is a Dialarc pedal it is a big lump Tried to sell our old DA, cooler & pedal all went in scrap bin 2 months ago just to big & heavy for the work we have now.
A proper wire wound rheostat in side, does it have a Hubble twist lock plug