Anachronism Mail Art Envelope Swap

From wikipedia: An anachronism—from the Greek ανά (ana: against, anti-) and χρόνος (chronos: time)—is an error in chronology, especially a chronological misplacing of persons, events, objects, or customs in regard to each other. The item is often an object, but may be a verbal expression, a technology, a philosophical idea, a musical style, a material, a custom, or anything else so closely associated with a particular period in time that it would be incorrect to place it outside its proper domain.