Rolls Royce Merlin Engine Piston and Con Rod

Perhaps the ultimate souvenir from the famous Merlin that powered the Spitfire, Hurricane and Lancaster in WWII. We suspect, looking at the condition, this one has never been used, although we have been advised it was probably for a Merlin XX engine. It is complete with fitted piston rings and believe this example would be hard to better. Diameter of piston 5.5" (13.5 cm).