Numismatic treasures await us in the most unlikely places. Take the 1870-S Half Dime, for example. According to official Mint records, none were ever struck, despite the fact that six pairs of Half Dime dies were on hand at the San Francisco mint. Yet, in early 1978, a single example of this previously unrecorded date was purchased as a common type coin. The exciting news of the discovery of an 1870-S Half Dime stunned the numismatic world and, following it's exhibition at the 1978 convention of the American Numismatic Association, this previously unappreciated coin sold for $425,000 to Michigan dealer John Abbott. How was the selling price for this unique rarity determined? -- by a formula agreed to in advance by all parties in which $25,000 was added to the hammer price of the 1804 Silver Dollar sold as part of the John Work Garrett collection!
Accounts of the discovery of the 1870-S Half Dime vary. One account claims the coin was found in a "junk tray", another says a "junk box" (same thing, actually), and a third says it was bought over the counter as a common type coin by a Cook County (IL) dealer.
The cornerstone of the second San Francisco Mint may contain another example of the 1870-S Half Dime along with an 1870-S Three Dollar Gold piece (which is known to have been placed therein) and possibly other 1870-S dated coins.
The following is a list of all 1870-S dated silver and gold coins and their reported mintages:
1870-S Half Dime - 0
1870-S Dime - 50,000
1870-S Quarter Dollar - 0
1870-S Half Dollar - 1,004,000
1870-S Silver Dollar - 0
1870-S Gold Dollar - 3,000
1870-S Quarter Eagle - 16,000
1870-S Three Dollars - 0
1870-S Half Eagle - 17,000
1870-S Eagle - 9,000
1870-S Double Eagle - 982,000
Examples are known of every denomination listed above except for the Quarter Dollar (could this be the next undiscovered treasure?)
According to Breen, the reverse of this coin was later used to produce 1871-S Half Dimes. He also lists the exact weight of this piece as 19.599 grains (1.27 grams) and the specific gravity as 10.316. The edge has 107 reeds.
Q. David Bowers noted a "microscopic raised line" on the upper left arm of Miss Liberty, wondering whether this might also appear on some of the Half Dimes issued by the Philadelphia Mint (since they were responsible for creating the dies sent to San Francisco).
Sources and/or recommended reading:
"Walter Breen's Complete Encyclopedia of U.S. and Colonial Coins" by Walter Breen
"The PCGS Population Report, October 2003" by The Professional Coin Grading Service
Description of Lot 1053 in the Auction '86 sale catalog
The Coin World website at http://www.coinworld.com
Harlan Berk's website at:
Numismatic News, May 11, 2004, page 52