It may well be a prototype. I remember seeing a 10x8 Thornton Tourist camera at a Camera Fair 3 or 4 years ago, it had an 8" wide roll film back, the lens board was missing, but they were round and tool 2 or 3 lenses, and you rotated the board to select the lens. The camera was made before Pickard joined and invested in the company. I have two unusual Thornton Pickard shutters that there's no mention of in literature, both came from close to where the company was located.
Prototypes were made and given to photographers to test, it's not unusual, but it is pot luck finding them as they are rare. In this case it's likely the winder never went into production. Remember that prior to the Nikon F the professional system camera with motor drives was the KW Praktina, and a choice of spring or electric motor drives and a bulk film back, also a huge choice of lenses from multiple manufacturers.
I'd do some digging around, it may well be worth a lot more than you paid for it.
Ian