It can be very litttle, infact one of the ones built at East Midlands Airport in the past the only original airframe parts was one leading edge and the data plate I believe, some indeed will come down to the data plate……….. It is very difficult to nail down an aircraft as “NEW” or rebuilt as in its service life it could and would have had wings, engines, rear ends and skins rebuilt or replaced, therefore the argument is none will be 100% original, even in Service.

However on the other Extreme Rolls-Royce’s MK19 that was built in the last years of the war has never had a major rebuild through out its life. It will have gone through overhauls etc, but taking it back to component parts and rebuilding it, it has not had that done. so is nearly original, well bar the Engne which is a hybrid based on a Shack unit with the gearing off I think a Firefly thrown in the front of it to convert it to a single prop, but looking at the wings, sometime in the past it lost its original fuel filler caps that were round for a different type.

Well said Tony