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Rob D.Last year one of the lots in a Mastro auction was five Butter Creams from Lionel Carter's collection. The description did not say whether these were the only five he owned, but I never saw another group of R306s offered by Mastro when selling the Carter collection, nor have I seen any singles show up. So my best guess is these five were the only ones he had in his collection.
Granted, they account for only one-sixth of a complete set, but they're all still together. I've upgraded a few but plan to keep them as part of my set.