I need to know what type of thermostat this model 68-105-8 would use. It has five wires from the unit and are colored red, black,black and yellow

What kind of heater is this?. and not to be picky, but you said 5 wires and mentioned only 4. Is this line voltage or low voltage? And that model number doesn't seem to come up anywhere in Janitrol information.

What kind of heater is this? ...and not to be picky, but you said 5 wires and mentioned only 4. Is this line voltage or low voltage? And that model number doesn't seem to come up anywhere in Janitrol information.

I had mentioned two sets of wires. I don't have an old thermostat to use as a guide line for a replacement. The four wires I mentioned come from the heater itself. The other five are the wires that go to a thermostat and power. I need the help in discovery of these wires. The wires in the heater go to the fan, transformer(24V), and a safety thermo device inside the heater next to the coils?? Not sure which one is the low voltage and high. My assumption is there is no low voltage since the transformer connects to the ignitor and no where else.
As you can read, Im not an expert in this heater. The other wires are two red, two black and one white. I am assumming that these wires connect to the power box and thermostat.
Thanks for responding