I've seen several single rounds of ammunition in years past, but even in the late 60's these were selling for $50.00 to $75.00 each. Back then you could buy an original box of .44 Henry Flat for $100.00, so the single round of center fire was very expensive. I still have a dandy model 1866 carbine in .44 Henry Center Fire that I aquired back in 1968 and which I lettered at that time. It was shipped from the factory on October 20, 1888. This is a very late gun in the 166XXX serial range. It is not recorded in the ledgers as being a center fire, although the conversion is definately factory. I don't know of any 1866's that are actually listed in the warehouse ledgers as .44 Henry Center Fire. I do know that late in 1891, just over 1000 center fire carbines were made up from left over parts and shipped to South America.