Nick
I've looked through my GE catalogs and finally found a JK22 - in my 1968 catalog. It's a double oven model with P7 self-cleaning in the upper oven, solid doors both oven? Could have been produced for a couple of years after that. I do not find that model in my 1972 catalog. I believe that the "H" in the model number indicates Harvest, which was introduced during the 1968 model year.
Hope this helps.
lawrence