Is This Some Kinda Trick Question, LOL?
"Sandy, what would be the difference between a JK-29 and a JK-28?"
Jeff,
Your question makes me wonder if you have found the model number JK 28 on that yellow double oven of yours.
If you have, it gives me some info I had not had before. If yours is a JK 28, that means that JK 28 is the number of the TOL double oven with two P*7 ovens, but without oven door windows. That configuration was sold in 1966, because GE hadn't yet begun putting windowed doors on the entire P*7 lineup yet.
A JK 29 is the exact same oven you have, but with windowed oven doors. The white unit you posted above is a JK 29.
So, it's looking to me like GE used JK 28 on the 1966 model, but changed it to JK 29 in 1967, when they began putting the windowed doors on the TOL double ovem. I have always referred to the 1966 version without the doors as a JK 29, for lack of any other model number; I do not have catalogs for every year. Dammit.
A check of my 1971 and 1972 catalogs shows that the model number JK 28 was not used for any of their wall ovens in either of those years.
So - are you telling me that your yellow oven is a JK 28?