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Adjusting, Adjustment

Adjusting, Adjustment.  Working a blank or partially struck piece, usually by hand, to proper tolerances of size, weight or temper prior to final striking. Adjusting the blank is a preparatory step for striking coins, it precedes all other preparatory steps including upsetting, annealing and metal cleaning of coinage blanks.

Adjusting coin blanks to proper weight was a common practice for precious metal

coinage blanks prior to the 20th century, particularly for mints with primitive equipment. It also continued for gold blanks even into the 20th century. Overweight blanks were shaved or filed of enough metal to reduce the weight to proper tollerance. Underweight blanks were rejected (as no adjustment could add weight).

The reason for blanks varying so greatly in weight was the lack of precision rolling mills. It was not until automatic micrometers were installed on mills that strip could be rolled to a precise thickness. Then technology for blanking became so developed in the last half of the 20th century that blanks could be created with precision to one thousandth of an inch. . Manual adjusting was no longer necessary.

How blanks were adjusted.  For more than a century weight adjusting was done manually with a file and a balance scale. In America this was done by women who would make the decision where to file each gold blank. With dexterous fingers they would file off burrs at the rim/edge juncture, and if more was required, from the circumference of the edge, or from the flat surface of the blank. Evidence of this filing seen on 18th and very early 19th century silver and gold coins, can sometimes be observed on the piece after it was struck. This is called an ADJUSTMENT MARK.

With experience, adjusters could judge how much to file off after first weighing on a balance. This done, the blank would be weighted again. It was necessary to reduce the weight within the prescribed tolerance. Mostly this was done for gold blanks (the salvaged metal could justify the cost of manual workers), but some large silver coins have been observed with adjustment marks as well.

The adjusters wore leather aprons to catch the filings, as the intent was to salvage

as much gold as possible while still providing legally prescribed correct weight blanks.

Even so, their clothing, sweepings and wash water were carefully processed to recover the tiniest speck of gold.

History of adjusting.  For hammer coinage prior to the 14th century some adjusting was done in the preparation of blanks. They had to be circular shape, the correct size and fairly uniform thickness. If not, another hammer blow was administered. But it was the demand for coins of close tolerance in the 19th century that gave rise to extensive manual adjusting after planchets were blanked in quantity.

The first gold coins struck at the recently established U.S. Mint at Philadelphia in 1794 exhibit adjusting. Breen states the first women hired at the mint were adjusters and that numismatists do not consider these adjustment marks on coin surfaces as impairments.

An account in 1853 told of 57 young women working in the adjustment room in the Philadelphia Mint. It stated that they adjusted 40,000 blanks in a 10-hour work day (requiring less than a minute per blank!). Coin making authority Dennis Cooper reports more than 200 adjusters employed in the Berlin mint prior to 1870, and shows an illustration of a dozen adjusters (of both sexes) working in the Royal Mint, London.

Cooper also illustrates a machine for mechanical adjusting (developed by Pilcher

and Jones, an English firm which made minting equipment). A quantity of blanks, perhaps 40 or 50 were placed in a roll. A circular file rotated as the blanks revolved around the file. The shavings dropped into a glass dish below.

In addition to this machine, Cooper also illustrates a clamp to hold blanks for manual scraping the surface, and two devices to do this mechanically. While somewhat ingenious, the first machine was, for the most part, impractical, since it could not customize the filing for each blank. It was far easier to do individual blanks manually, with or without the holders shown.

Mechanical balances, invented by Austrian Ludwig Seyss in 1871, dramatically[RWB1]  affected adjusting. Prior to this time all weighing was done manually. After 1871 weighing could be done ten at a time on Seyss automatic balances with tolerances set to sort blanks in three hoppers: under legal limit, within legal limit and over legal limit. Later improvements on mechanical balances were made by the Philadelphia Mint and put into daily operation in 1910.

Labor costs were such that it was cost effective to adjust only gold overweight coin blanks early in the 20th century. Otherwise precious metal blanks over and under legal limits were sent back to the furnaces to be remelted.

Modern adjusting.  Overweight blanks intended for gold coins, medals – or bullion coins! – are just as much a problem in the 21st century as it was in the 19th century. Once planchets have been blanked and weighed, the overweight blanks are separated, then rolled diagonally across a fast-moving belt of aluminum oxide. They are weighed again to check tolerance and if still overweight they are treated again. The dust from the aluminum oxide belt is salvaged as coinage alloy gold.

Temper adjusting of medals.  Adjusting to temper is somewhat more difficult than shaving or filing off metal. Heat treating will alter the temper, but in some instances, as in the case of die draw, where the metal flows into, then out of a die cavity in succeeding strikes during multiple striking, the temper must be adjusted – by sharp hammer blows to the edge of the partially struck piece! The hammer blows impact the flash (later to be removed) but this jolts the surface molecules enough to allow the metal to flow back into the die cavity during the final press striking.


C66  {1988} Cooper, p 202-04.

CH5 {1853} Anonymous.

NC8 {1988} Breen, p 373.

excerpted with permission from

An Encyclopedia of Coin and Medal Technology

For Artists, Makers, Collectors and Curators


Roger W. Burdette, Editor

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