We have a 1977 Model 412 Litton oven. It's a Vari-Cook design and that cookbook you have is the one that came with ours.
Some Littons DID come with a glass removable floor. The way to tell if yours is one of those look at the floor of your oven. Does it have a depression in the floor that would hold about 1/2 of a quart of water? If you do, yours came with a glass plate. The metal floor models were totally flat. Ours had the glass floor which shattered one time while popping microwave popcorn. The glass for this oven has been totally unobtainium for years now. The best way to handle it would be go to a glass place and ask for a tempered glass plate about 1/4" thick in the size of the oven floor.
A guy in a microwave repair shop once did say that Litton came out with a conversion kit to convert the glass floor to a metal floor. All the kit contained was a flat teflon coated piece of metal and some silicone sealant. But with everything being so throwawayable these days I imagine these kits are in the same
situation the glass bottom plates are.
We last used ours about 4 years ago when our Kenmore MW died via power surge. It still works, but is definitely slower than our 1100W GE oven we have now. I believe the Litton's are rated at 750W.