The pictured reloader is a very early Pat. Pending machine. I have one that is nearly identical with a Bronze powder slide housing like the one pictured. Mine does not have a powder shut off.
It should be noted that a No. 0 powder slide is not used with this powder slide housing. The powder slide is 1/2" wide rather than 5/8" wide. I have another Pat. Pending machine that uses a standard No. 0 powder slide, but the housing is not marked as such. I'm guessing it predated the development No. 00 powder slide housing so there was no need to distinguish between them. Although Star reloaders remained largely unchanged for many years, there were quite a few changes in the first few years.
The machine itself is not a prototype. It is definitely a commercial model, and not the earliest commercial model which would have had a cast iron rather than an aluminum base. As for the shut off, I don't know if it is something Star tried then abandoned or if it was user installed.
Bruce Williams
PS My early Star was given to me by the late Larry Lawson. He was a great guy with whom I spent many hours talking on the phone. That alone makes this machine a cherished part of my collection.