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Watershed Dates in the Modern Minting Process

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 by James Wiles, Ph.D.

CONECA Master Listing

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Watershed Dates in the
Modern Minting Process

1909 The beginning of the modern minting process is set in 1909.  Prior to 1909 a partial hubbing process was utilized by the U.S. Mint.  This process left the date and mintmark to be hand punched into each working die.  1909 saw for the first time, the date engraved into the master die, so that every working hub and working die carried the same date positioning.  Mintmarks, however, were still applied to the working dies by hand as each branch mint had a need for dies.

1985 The U.S. Mint began punching the mintmark into the master die for all proof coinage.  The last year possible for an RPM on a proof coin is 1984, however, the last known RPM for proof coins is 1975.  In the middle of 1974 the S mintmark punch broke and a new punch with a new style of S was placed into use.  This new punch was itself doubled resulting in a doubled mintmark on every working die.  The doubling on the new punch wore off fairly rapidly so even though the punch was used into 1979 the doubling is no longer seen after 1976.

1986 The U.S. Mint began experimenting with a single squeeze hubbing process. This process eliminates the need to anneal a die and then re-hub it in order to get the proper depth for striking coins.

1990 The U.S. Mint began punching the mintmark into the master die for the cent and nickel denominations.  The last year possible for an RPM on a business strike cent or nickel is 1989.  There are several known RPMs for the 1989-D cent but the last known nickel RPM is dated 1984-D.

1991 The U.S. Mint began punching the mintmark into the master die for the dime, quarter, and half dollar denominations.  The last year possible for an RPM on a business strike dime, quarter or half is 1990.  The last known RPM for a dime is 1988-D.  The last known RPM for a quarter is 1989-D.  The last known RPM for a half dollar is 1989-D and can be found in Mint Sets.

1996 The Denver Mint opened its own die shop and began using a single squeeze hubbing process for cents through quarters.  Thus the doubled die was effectively eliminated.  There are a couple of ways for doubling to occur on the die during the single squeeze process, but the vast majority of doubled dies are now a thing of the past.  There are some 1996 dated doubled die obverses on the Philadelphia cent.

1997 The Philadelphia Mint began using the new single squeeze hubbing process for cents through quarters.

1999 The U.S. Mint adds the half dollar to the single squeeze hubbing process.  The last known doubled die for the half dollar is dated 1992-S and is on the silver proof.

1999 The U.S. Mint used the old hubbing equipment to create the SBA dollar coins needed late in the year and for collector proof sets.  A couple of nice doubled die obverses are known for the 1999-P proof SBA.

 

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Copyright James Wiles, 2016

Email: jameswiles@sbcglobal.net

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