Die Alignment. Positioning or orienting a pair of dies – obverse and reverse – so the axis of each matches perfectly. Dies cut on round diestock have the ability of being rotated, and thus need to be oriented during setup. Pieces struck from dies at this time, die trials, may show a perfect alignment, or more often, show an axial misalignment until they are correctly positioned. A struck piece with an imperfect alignment is called a rotated die.

Alignment on struck pieces is expressed by arrows in numismatic literature: the axis is shown from the bottom up, expressed as ?. Medals are usually ?? (called medal turn, top of obverse is directly opposite top of reverse); coins are usually ?? (called coin turn, top of obverse opposite bottom of reverse). There are exceptions, of course. See axis (where a shortened form of expressing alignment by the omission of the first arrow is illustrated).

Keying dies for alignment. On die alignment of very critical register some form of keying is employed. This can be as simple as drawing, scribing, or painting a line – guide mark – on the side of both dies. Dies are placed in the press where these lines can be observed and are locked in their chucks so the two dies are lined up exactly. Pieces struck at this time should have the desired die alignment.

For open face dies a very exacting form of keying can be employed: guide pin

and bushing. A hole is drilled in the face of both dies (outside the image, of course) directly across from each other; a guide pin is inserted in one and when the dies are mated the pin should enter the bushing lining the hole on opposite die for critical register. During striking the guide pin can remain (if not in the way of feeding the blanks) or be removed.

Dies cut on square or hexagonal diestock usually do not need a critical register for both dies as the alignment is left up to the diemaker to cut the die precisely square with one side of the diestock (the pressman can easily obtain die alignment during setup by manually positioning the square or hexagonal diestock, but could, conceivably be 90°, 180° or 270° off alignment for square stock).

Rotated misalignment. Where struck pieces show rotated misalignment, particularly in the coining process with dies on round diestock, this is a result of: (1) incorrect setup, a human error of ineptness or malfeasance; or (2) loose dies, which may cause a chattering of the dies, which will eventually cause a struck piece with rotated dies. The later is a mechanical error, no matter how tight the dies are locked in their chucks, some vibration may loosen these causing the dies to rotate.

Coins with the alignment of ?? – called the 6 o'clock position – usually have the most common misalignment at the 12 o'clock position (?? ), undoubtedly due to incorrect setup, followed by 5 o'clock and 7 o'clock, slight rotating from the standard position, other positions follow with 11 o'clock and 1 o'clock the rarest positions of all (there are exceptions, of course).

Die Alignment of United States coins. Coins exhibiting misalignment due to any of the above causes exist in every decade of United States coining. It is not peculiar to one mint or the size of the dies and coins, nor to the kind of composition. Coins out of alignment can occur during any coinage with dies made of round diestock. While coins from large press runs may be apt to have dies working loose, even this is not exclusively a reason for their existence.

Numismatic cataloger Walter Breen mentions only 18 U.S. coins with incorrect die alignment in his encyclopedia of U.S. coins. Most of these were for important coins (like the Confederate half dollar, Breen 8001). He completely omits mention of any Lincoln cent misalignment, yet these are so common, special collections can be made of these. Breen does relate, however, that 1983 Olympic Dollars of 1983-S in proof rotated 180° were caught and destroyed by mint officials before they were issued.

Some collectors make a study of rotated dies; while not that important an aspect of numismatics, it is an interesting bypath of numismatic study.

References:

NC10 {1988} Breen.