In response to his email, Phil ~bikerguyflip sent me this information.
"Ben Smith drove it to a church function and we rode with him, my dad and he were good friends. I don't even know how I remember the designation, everyone denied it ever existed. I don't know of any photos of the XE1500. Ben Smith had a website a few years ago (no longer available I found) where he made reference to it, not as the XE1500 but as a Mark ll retractable hardtop he had built at Ford. After leaving Ford he and his youngest son, Dave, founded a company that retrofitted Mustangs with manually operated retractable hardtops... Ben was ten years younger than my father. A very interesting man another engineer, Bob Studt, came to church with a 1955 Ford. It had a barn door hasp bolted on the hood with a padlock. He would not open the hood but told me it had a free piston engine, a type of compressor the Germans developed for their submarines. I believe Ford was driving a turbine with it. Bob was quite tight lipped, always. I think Ben may be still alive in his nineties, living in Arizona, Google him, you will find it very interesting...he had a lot to do with the design of the Thunderbirds. Phil Draper."
Here are some additional links you might find interesting.
1957 Ford Fairlane Skyliner Retractable Hardtop...1965 Ford Mustang With Retractable Hardtop... Continental Mark II With Retractable Hardtop...
The Retractable Hardtop story as told by Hemmings Magazine....