Collector castings and limited finishes — the designs produced in small numbers rather than run continuously. This is the shelf to check if you already own a few and want something that is not in everyone else's collection.
Said plainly, because it is the one thing worth knowing: rare means scarce, not better made. The foam, the age rating and the finish quality are the same as the core range. What you are paying for is that the casting is not repeated — which also means that when one of these sells out, waiting does not usually bring it back.