Hey Money, don’t know where your finding these odd ones, But when Marsal Got wanted by chains like Sabbaro, they sold from the family and dropped the steam tables. I found heaters, both 208V and 240V, and a wiring diagram. But nothing as far as a parts break down or controller, float switch, high limit, or Thermistor.
Depending on the mounting and water height, and whether it is magnetic reed or mechanical float with a micro-switch, You might find a replacement.
Personally I would get out my multi-meter and find out what is wrong with it. It’s a very simple system. The temp controler will have been made by another company and you might find numbers on it for a replacement