It's Stephenson's Warmlite.
Yes it was called Filmgap , also spelled Film-Gap.
There is a brief description of it in a 1973 Popular Mechanic magazine (Google "Stephenson's Filmgap Popular Mechanics")
Possibly drawings and pictures were lost in the 1982 fire that burned down the family house.
Bruce B Johnson at :
I have an even earlier picture of the Model 1, "Original Filmgap tent," dated 1958
Maybe you should ask him.