Judd-1547 is the copper version of the legendary Judd-1546 (the unique gold $50 "Union" currently housed in the National Numismatic Collection at the Smithsonian Institution). The copper version is a great rarity in its own right, and is highly prized by collectors as the only option to own this pattern design. Several examples have been gilt (or gold-plated), possibly at the Mint or done privately; these are listed on PCGS CoinFacts under PCGS number 861891.
William Barber designed two versions of the $50 Union both sharing the same reverse but differing slightly in the size and shape of Liberty's head on the obverse. Though not as rare as some patterns, the copper and gilt-copper $50 Unions are exceedingly popular and quite difficult to locate The finest J-1547 appears to be the PCGS PR64BN example that once belonged to William Woodin, F.C.C. Boyd, and which last appeared at auction in August 2011.