There is an actual GMC part number for the heater: GMC-3117868 The Harrison PN *appears* to be H-441-? where ? is a letter.
The kit it was part of did have its own designation: SSL-1276
The manual I have a copy of shows the heater but with different mounting brackets. So I am assuming that it was customized for GMC trucks. The manual is dated 1944 but I would bet they go back farther... and that is what I am trying to resolve:
When did the H-441 start production? 441 might be a date, but I have verified the numbers on the Harrison tag for two Chevrolet Super Deluxe Harrison heaters and they are the same. So either its a part number H-02-46 or the dumbest luck in the world I found two identical heaters made in the same month 70+ years ago.
It would be interesting to find a brochure or parts book that actually had the heater in something other than a Willys. Seeing that they did pop up in Chevy cars and GMC vehicles.
But the one, single thing I am trying to resolve is when the presence of the stamped boss in the lower right side appeared. The manual I have doesn't show the boss, every other Harrison model I can find does show it. The boss is for the knob that controls the passenger side baffle. The specific unit I am researching does not have any interior baffles, and no control knobs. So why would it have the boss?
My explanation is that the simplified Military version was the 'initial' models (early/mid 40's) did not have the boss/baffles, and that a 'proper' military heater would be without the boss (as it shows in the install manual). But like so many other hobbies unless you can prove it, most people will go with what they see... later models, with the boss, as being proper.
