I recently had a pair of plaster casts said to be from the estate of sculptor Adlai Stevenson Hardin. Hardin made the plasters which were eventually made into medals by Medallic Art Company (MACO) sometime in the 1980's. The plasters were about eleven inches in diameter and hands down the most fragile items in my collection. The medals were for Skylab I and II. Skylab was sandwitched between the Apollo/Space Shuttle era and quickly forgotten. You could call the missions an early attempt at space stations. I love space mission exonumia and you could write a book about it, there's just so much out there.