ORIGINAL: HighPlains
As originally used in the drones, they ran 12-5 Rev-Up props that did not have the logos printed on the the blades that the commercial props had. The props had a 12-5 marking on the hub. One production run was for around 10,000 props.
The two engines I have came from the most recent set of kits before they discontinued the program. The sealed boxes were dated September 1990. I still have 2 props somewhere, but they had no markings of any kind. I'm not 100% certain on the pitch, but they were 12" dia. If I can find one of them, I'll spin one up and compare the rpm just for the heck of it.
I'll have to see if I can find something to use as a sleeve and try my ST carb to see if my engine runs any better. The neck of the k&b carb is .623" and the st carb I have is .590".