NNP

Weights and Weighing.  Standards and process of determining weight (mass) of a numismatic item either before or after it is manufactured. When mints accepted metal to be coined, prior to the 20th century, weighing the metal was important. Mints prided themselves on having large balance beam scales that were extremely sensitive. Some of these scales could distinguish a fraction of a gram in a 5000-gram weighing. These sensitive scales had to be custom built, usually within the mint, as commercial scales were not manufactured until mid 19th century. When metal was received at mints, it was weighed in total and again in small assay samples (to determine purity). The metal was weighted when formulated into the alloy, then not until the metal was rolled and blanked. At this stage coin blanks had to be weighed before striking to eliminate underweight and overweight coins – more so for gold and silver coins than for bronze – giving rise to automated scales that could make repetitious weighings on a production basis.

Coinage laws usually specify the tolerance of weight for coins, both precious metal gold and silver, in addition to minor coins. Thus at every mint, weighing occurred at several steps of coin making prior to manufacture, as a supplement to certify counted pieces afterwards, and finally as a test of metal content or authenticity after the coins left the mint.

Adjusters each had scales at their workbench and would file off metal of overweight blanks to bring them to within tolerance (the filings would then be salvaged). At the U.S. Mint a room full of women performed this adjusting operation using dozens of scales. Automatic weighing machines were developed in 1871 by an Austrian, Ludwig Seyss, and were in most mints by the mid 1880s. But manual weighing continued even into the 20th century.

After the coins were counted, and the determined number set aside for a bag, they would be weighed in mass to check again on the precise weight for the correct number of pieces.

Weight standards.  Up to the 18th century the standards used for weighing varied widely by local, by commodity, and sometimes by who was doing the weighing. Each city had its own weight system. A standard for metal would be different from a standard for grain, or food or cloth. A royal scale would be different from a commercial scale even in the same city (taxes would be paid on the heavier royal scale!).

A dual-weight system still exists in Great Britain and the United States to this day. Gold, silver, jewels, liquors and pharmaceuticals are weighed by the troy weight (24 grains in a pennyweight, 10 pennyweights to an ounce, 12 ounces to a pound).

All other goods are weighed by avoirdupois weight (437 1/3 grains to an ounce, 16 ounces to a pound). In both these standards the grain is the same exact weight, the ounce and pound are different. Small weights of precious metal (as gold) are expressed in pennyweights (abbreviated dwt), to be obvious the troy measure is indicated. The use of "ounce" is ambiguous unless it is stated troy or avoirdupois.  (See Chart, Measurements and Weights, Appendix 5).

The French adopted the metric-decimal system in 1799 shortly after the French Revolution. This system has many advantages over either the troy or avoirdupois systems. Its decimal basis can be expressed in larger or smaller measurements by moving the decimal point.

The metric system has been adopted for all scientific measurements, and for commercial transactions in virtually the rest of the world (except Great Britain and U.S.). It has a similar word – grams (the French word is grammes) – like grains for a small unit.  Thus coins and medals are weighed in troy/avoirdupois grains or metric grams.

History of weighing coins.  Coins of precious metals have always been weighed at every transaction unless both parties were convinced they knew the coins were standard. Even so, known coins could be short weight. They were tested on scales against coin weights (see box). Oriental merchants and bankers would mark coins with a private chopmark indicating they had weighed and assayed the coin, attesting to its weight and fineness, despite the fact their may have already been hundreds of chopmarks already on the coin.

Moneyers creating hammered coins were required to pro- duce an exact number of coins per pound. This weight concept existed among private makers of tokens in England and carried over to the American colonies. Coins were designated so many per pound. Breen gives details on this in the Metrology section of his Encyclopedia of U.S. and Colonial Coins. In the 20th century, however, the weight of coins are specified by a precise weight, in grams (metric), per single coin.

 Coin Weight.  A stamped metal disk inscribed with its    

 weight the same as a coin for use on a balance scale to  

 attest the full weight of a single coin. Usually these   

 were for gold coins to test that none of its metal had   

 been removed and that it was full weight. Early coin     

 weights were made to resemble the coin they were to test 

 (because even people who could not read could check the  

 scale).  Most were made of metal but some were glass     

 (called glass coin weights).  Later coin weights were    

 sold in sets housed in wood cases, often with the balance

 scales. Coin weights were made of brass, bronze, lead    

 (in addition to glass). Those in sets often had knobs on 

 the top to lift them. Coin weights were used in areas of 

 great commerce, but are noted for those manufactured in  

 China, Germany, France and England. Some were marked by  

 their maker with a hallmark or mastermark.                                                                          

References:                                                                                                                               

X11    {1965} Kisch (Bruno)  Scales and Weights, An Historical Outline.  New Haven and London: Yale Univ Press.

C67    {1988} Cooper, pp 202-207, illus.

NC12 {1988} Breen, p xiii.

excerpted with permission from

An Encyclopedia of Coin and Medal Technology

For Artists, Makers, Collectors and Curators

COMPILED AND WRITTEN BY D. WAYNE JOHNSON

Roger W. Burdette, Editor