There was also an instance where in the early 90s, in hockey, Topps released the Gold parallel set. Instead of including a gold parallel of the checklists, they created cards of players that didn't have cards in the base set, some (if not all) of them were rookies, and they are allowed the RC tag. It is a very rare exception when a parallel or an insert gets the RC tag. Generally speaking, the older sets on here have already been tagged properly, so no need to revisit. Newer sets will be a lot more clear cut.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).