It is the description used by Bloomington Gold in the USA for Corvettes, and has spread to other marques. It doesn't cover rubbish, the car still has to retain 50% of its original paint, trim, underbonnet etc. Anything replaced starts reducing the %. My Premier barely qualifies and it is in very good condition. But it has had some things replaced, like water pump, some hoses, radiator (early on with a genuine one), head gaskets, muffler, mudflaps, tyres, shocks etc. In some areas it is down to 55-60% factory original.