Mica Insulated Strip Heater, Heater Voltage 120V AC, Overall Length 6 in, Mounting Dimension 5 3/8 in, Element Width 1 1/2 in, 100 W Watts, Watt Density 23W/sq in, Terminals Tandem at One End, Sheath Material Rust Resistant Coated Steel, 1 Phase, Max. Sheath Temp. 900 Degrees F, Slotted Hole Length 9/32 in, Slotted Hole Width 3/8 in, Screw Size 10-32, Standards UL Recognized

There was a totally different concept for the internal support system of the frame.  It was initially going to use steel grid pattern, but we discovered that it would make the wiring near impossible to thread throughout the heating elements.  The Elements were also on a great sale at the time.

https://www.zoro.com/tempco-ins-strip-heater-120v-6-in-l-900-deg-f-msh02260/i/G2033193/#specifications

The first iteration of the BAD setup.