No total of Grandma and Grandpa are known. The '76 doors were only sold in 1976 and the early '77 still had the stars, but missing the 76 in the large star on right door.
Seems the Grandpa doors had the old style large trees and the Grandma had the shorter trees. I've never seen a different 76 Grandma door pattern as shown below;
When the trees were added to the doors, the tall type were on the single door stoves and later Grandpa. It's like these short trees were the new style to come. BUT, here's an early Grandma with 3 piece top and the first doors without drilling hinge pins through. Even this early Grandma had the newer style trees. They didn't match Grandpa ! Can't answer it.
Notice fabricator supplied handles and caps. These handles were common from this fabricator for a time.
Another view showing 3 piece top;
(no, the stove board pad isn't large enough)
Perhaps Grandma came out later in the year than Grandpa using a foundry pattern made with the new style trees and they didn't make new patterns for Grandpa to match. Bob may have been so fed up at this point with doors, he didn't care as long as they worked!
It's difficult putting together changes as the stoves evolve differently made by fabricators that made the boxes to specs, ordered doors only, and had their own ways of finishing the product. (when the puzzle is put together, I use these differences to determine where the stove came from) It's not like a product that comes from a single factory or another division of that manufacturer making the same product. In '79 there were 42 makers across the US and Canada. When they started out, they couldn't make stoves fast enough. First came the stoves, which caused the need for safe installation procedures. Then insurance regulations, laws were drawn up for testing (which weren't standard across the US using 4 different testing labs since the state laws didn't recognize testing from other labs) and then smoke regulations became necessary with so many in operation. As Fisher International was formed, things became standardized so it becomes easier after 1978 when the testing standards used and all fabricators were under the same direction. It's more like putting the history behind each fabricators business together and finding where the different ideas came from that was behind the changes company wide. Combine all the changes being made by different fabricators making 15,000 to 25,000 stoves across the country a MONTH, businesses changing hands, some cutting corners to improve their bottom line, reverting back to the original owner in many cases............. You can only generalize when changes took place since they happened at different times across the country. Then add the fact that anyone with a garage and welder could make a stove and sell locally under the radar when the price of oil was going crazy and even being rationed. Some licensed builders would make their own version of plate stove and when Fisher came down on them, revoked their license, they would sell their doors to the competition or people building their own stoves.
I can speculate on a lot of origins of their products and ideas, but try to only answer with documented proof. Then something surfaces to contradict a document or proof.
I think I have more questions than everyone has asked combined !
Steel plate doors would only be from Oregon, possibly marked FSSO in weld on the bottom.
Yes, my steam hobby turned into a job on an excursion RR which included rebuilding and maintaining steam locomotives and equipment. After retirement from my own business, I rebuilt a few stationary engines. (they are more common and cheaper than traction engines, rollers and rolling equipment) Never got into miniature or model steam, only full size. The price has gone as crazy as Fisher Stoves in the last 10 years. A friend of mine that recently died had a "skimmer" that is a forerunner of a modern day backhoe. More like a cross between steam shovel and excavator. That's the kind of "stuff" I make parts for and work on. The green outrigger (foot) in the front is 6 inch pipe casing. It's BIG.