The definition of "proof" within the lexicon of American numismatics is surprisingly controversial. Does any sharply struck coin with exceptionally mirrored surfaces qualify as a "proof?" Is the coiner's intent also required to confer proof status? An anonymous Newman Portal user recently searched on the term "one-sided proof."

NNP identifies sixty auction lots so described, the earliest being in the 1950s New Netherlands catalogs, and we can thus likely attribute the modern popularization of this term to Walter Breen, who worked for New Netherlands during this period. The term is more frequently associated with large cents of the 1820s and 1830s than with other denominations, and the cataloger of that series, Harold R. Newcomb, wrote of these coins "obverses are perfection, but reverses have the usual mint bloom as found on pieces coined for circulation."

Stack's Bowers sales of the Twin Leaf collection (July 2015, lot 2262, an 1835 N-13 large cent) is a typical example. The coin has a storied pedigree including Beckwith, Newcomb, and Naftzger. While PCGS declined to certify the coin as a proof, the catalogers are united on the physical description, with the Goldberg's attribution being the most succinct: "Proof-60 obverse, MS-62 reverse." The fact that varied issues in this era are known with proof-like obverses and uncirculated reverses (and not vice versa) certainly suggests intent on the part of the coiner. We look forward to John Dannreuther's upcoming multi-volume work on United States proof coinage, which will hopefully shed additional light on this question.

Link to NNP auction catalog search for "one-sided proof":
https://nnp.wustl.edu/library/advancedsearch?
contenttype=Auction&title=&author=&publisher=&searchlow=
&searchhigh=&fullsearchterm=one-sided+proof

Link to Stack's Bowers Twin Leaf collection, lot 2262:
https://nnp.wustl.edu/library/auctionlots?AucCoId=3&AuctionId=517107&page=141

Link to Harold R. Newcomb's United States Copper Cents, 1816-1857 on Newman Portal:
https://nnp.wustl.edu/library/book/526320