I've just spotted this ULTRA RARE RCBS 1967 scale on ebay. According to the description this model was never offered to the public for sale.
My guess is, and it's only a guess, is that this scale looks like it has some sort of mechanical damper. I believe this was just about the time when the first magnetic damped reloading scales made an appearance. With the magnetic damping being such a game changer I'm thinking that RCBS decided not to go ahead with something that would become obsolete almost overnight.