Spain
Provisional Government copper Specimen Uniface Trial 100 Pesetas 1870 SP64 Brown PCGS, Madrid mint, KM-Unl, Cal-Unl (however patterns in copper are mentioned on page 806 and considered "rarisimas"). A spectacular copper trial strike for the obverse of the gold 100 Pesetas of 1870 with "PRUEBA" stamped on the reverse. Featuring the statuesque figure of Hispania with the Pyrenees behind, this Specimen glows with reddish-tinged chestnut surfaces that brighten into a lustrous champagne hue upon rotation. The trial for which this piece was made--modern Spain's rarest gold issue, perhaps one of the world's--asserts a reported mintage of just 12 pieces. Of that scant figure, roughly 10 examples have surfaced in auctions over the past several decades, with the most recent example sold by Numismatica Ars Classica in their May 2012 auction which hammered for just over $190,000. Taking into account these factors, it seems to follow that this trail strike for one of the most elusive gold coins from the modern era should also be worth a substantial premium.
Estimate: 5000-7000 USD