Dave:
"I've reached the conclusion that both of mine are missing their under lid interior tool trays."
If you'll look at your machines, you'll see slots on the top of their lids- the ones you thought were for a "tool fence".
Those are your clue that your models used the exterior tool tray shown in several photos here- it fit on top of the lid. They are not easy to find, because they were vulnerable to damage. They had little hook-shaped tabs on their lower edge; the tabs fit the slots on the lid. Many of them had their tabs broken by people who wanted to remove the tray for some reason, and didn't know how. You had to slide the tray towards the front of the machine, then lift up. Even then, the tabs could break, because they fit the slots so tightly. When I had a Sears Best machine, it came with a broken tray. After a few months' hunting, I found a parts machine with a good one. For some odd reason, Sears evidently didn't consider the tray to be part of the machine, but rather, part of the accessories. When they did catalogue photography on these machines, notice that the machine was photographed without the tray, and the tray depicted as one of the attachment items. I guess the tray hid too much of that luuuuuuvly fake woodgrain.
I remember that Sears' term for the tray was a "tool garden", at least for a few editions of the catalogue.