Repunched Mint Mark (RPM)

What it is

Until the early 1990s, mint marks were punched into each working die by hand. When the punch was applied more than once in slightly different places, coins show a doubled or tripled mint mark.

What causes it

Multiple hand blows with the mint mark punch.

How to identify it

• Look under 10x for a second outline around the mint mark.
• An over mint mark, such as D over S, shows a different letter beneath.
• The variety is consistent on all coins from that die.

How to tell it from damage

Machine doubling can blur a mint mark. A true RPM shows a separate, distinct impression of the letter.

How mint marks were punched by hand

For most of US Mint history, master hubs and dies carried the design but no mint mark, because the same design was used at several mints. Each working die meant for a branch mint had its mint mark added separately. A worker held a steel punch bearing the letter in position and struck it with a hammer. Getting a deep, clear mark often took several blows. If the punch moved or was lifted and set down again between blows, the die ended up with two or more overlapping letters.

The Mint began putting the mint mark into the master die for proof coins in 1985 and for circulating coins in 1990. Once the mark was part of the design hubbed into every working die, hand punching ended and new repunched mint marks became almost impossible. Nearly every RPM is dated before 1990.

Because Philadelphia coins carried no mint mark before 1979 apart from the wartime nickels of 1942 to 1945, RPMs are found mostly on coins from Denver, San Francisco, New Orleans and Carson City.

Kinds of repunched and over mint marks

Collectors describe a repunched mint mark by where the extra image sits relative to the main letter: north, south, east, west or a combination such as northwest. A punch turned between blows gives a rotated RPM and a punch held at an angle gives a tilted one. A mark punched three or four times is a triple or quadruple RPM.

An over mint mark, written as D/S, shows one mint's letter punched over another's. It happened when a die prepared for one branch was sent to another and re-marked. Known examples include the 1938-D/S Buffalo nickel, the 1944-D/S Lincoln cent and the 1955-D/S Jefferson nickel. A horizontal mint mark is a letter first punched sideways and then corrected, as on the 1909-S over horizontal S Lincoln cent.

Catalogs number each RPM die separately, in the CONECA listing and in the Cherrypickers' Guide, because a single date and mint can have dozens of different RPM dies. Lincoln cents from the 1940s to the 1960s, Jefferson nickels and Roosevelt dimes from the same years are especially rich hunting grounds.

Examining a mint mark step by step

Use a 10x to 20x loupe, because many RPMs are only visible under magnification. Rotate the coin under one light and look for a second outline inside or beside the main letter. On a D, look for a second curve inside the opening or a doubled upright stroke. On an S, look for extra serifs at the ends of the curves or a second curve through the center.

Check that the secondary image is raised, with its own edges, even when it is partly covered by the main letter. Then match the coin to a listed die by the direction and spacing of the secondary mark and by other markers such as die cracks or the exact position of the mint mark relative to the date.

RPMs compared with machine doubling and damage

Machine doubling flattens one side of the mint mark into a shelf, making it look thick or doubled. The shelf is lower than the letter and runs in the same direction as shelves on the date and legends. A true RPM can show its secondary letter in any direction regardless of the rest of the coin. The rest of the coin often shows no doubling at all.

Damage can also confuse the picture. A pin or tool pushed against the mint mark leaves a scratch or dent, not a letter shape. Some altered coins have had a mint mark added or changed, a concern for key dates. On those, look for a seam around the letter, a slight color difference or a letter that does not match the punch style used that year.

Punch styles and what they reveal

The shape of mint mark punches changed over the years. San Francisco and Denver each used several distinct styles of letter. Knowing the correct punch for a year helps confirm both RPMs and over mint marks. The hidden letter in an over mint mark should match a punch the other mint was using at that time. An added mint mark often gives itself away by being the wrong style for its date.

Grading and attribution

Grading services will attribute listed RPMs on the holder label when the submitter requests it, usually with the catalog number. Strong, widely spaced RPMs and over mint marks draw the most interest and carry the clearest premiums. Minor RPMs that need high magnification are collected mostly by specialists, who value them for completeness rather than visual impact.

Frequently asked questions