Here you find unusual automobiles: Very original classic cars at various auctions. Originality typically comes from the interior of a car (not flawless, but original), a clean, unmolested engine bay (with the original engine of course), a trunk area with the original lining/interior, original steering wheel and dashboard. The paint doesn't matter match (though original paint is a plus of course.)

I judge the originality from my photo archive of the manufacturers, but also comapring photos of other cars that have been for sale in the past. Bad interior, bad overall condition doesn't matter. These cars are the best source as a reference.

Also useful as a resource, but not necessarily to research originality, are classic car ads like the collections of graphic ads at the oldsads collection and others.