I think the first category 'Sierra RS Cosworth' will be a mix of 3dr, RS500 & the early Sapphs as they were badged as plain old Sierra RS, and as you can see that in 1994, 4845 were licenced which is pretty much the entire 3dr production run, and I'm sure many would have died before then.
After about 1990, I think they started being called Sierra Sapphire RS Cosworth ( I stand to be corrected if anyone knows better)