Maybe it's original application was horizontal bench mounted for laboratory or military purposes. I saw incredible optics on benches once in a military reutilization disposal organization that was intended for auction. Along with the electronics it filled a good potion of a ware house. To my dismay, on my next visit, I found that it had been demilitarized because it was sensitive classified equipment as a complete unit. Optics were shattered.
Maybe a bench-mounted Goto Coelostat?