Sure did use a propane torch, that was my first instinct.
Heater is a Modine PD 100AA0111 - Age is unknown, building is ~30 years old, but unknown who/when it was installed.
Red hot, pilot lit, release button - gas turns off.
Voltage at gas valve like that goes well above 30 during propane heating.
Thermocouple seems correct, it is appropriate for the gas valve mfg. Not a OEM product, but still I think an appropriate thermocouple replacement.
Swapped back to the original one anyhow, as I think it is a higher quality product, and generates good numbers on the meter.