I saw it at on Display at Comic Con. About half the size of the regular SS model. Brandon from Prop Store said it was from someone that worked at ILM on ROTJ. My guess would be that it was a background model that needed to go or be far away from camera. Or as a background model to be shot behind a larger scale foreground one (less likely). So a smaller model would be better for that sort of shot. Maybe for the shots where the Rebel fleet is shooting straight away into hyperspace for the final battle.