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Diestock.  The metal from which sections are cut and used to make dies. Diestock is customarily round (bar stock), but hexagonal, square, or in the case of bar dies, rectangular stock can be used as well. The sequence is as follows: die blocks are made from diestock; die blanks are made from die blocks; dies are made from die blanks; coins and medals are made from dies.

Diestock is ordered to prescribed specifications: (1) diameter (in convenient lengths of about 6 feet), (2) the kind of carbonized steel, (3) hardness desired, and (4) type of steel desired for the kind of heat treating to be employed for that metal (as oil or water). Obtaining the best steel possible in the beginning will eliminate problems later in use (of dies chipping, breaking or sinking). The sections are cut on a band saw, slightly oversize of intended depth. Then considerable preparation is done in the tool and die department to surface grind both top and bottom surfaces – they must be true and parallel! At this stage the dies can be engraved or machined cut (as in a die-engraving pantograph). Or the dies are then placed on a lathe and machined to required shape of a cone blank or dome blank. This is polished smooth. The die blank can then be softened by heat treating and hubbed of the required design.

Specialty steel, as diestock for machining dies, is a product of the 20th century. Previous to 1900 the steel to make dies was die forged. Iron was treated and combined with carbon to make steel, then it was tempered, hammered and heat treated many times to harden it (like making the steel for a sword blade).

Large users of diestock, like Scovill in Waterbury, would order diestock from die forgers in the region who specialized in treating steel. They also required the dieforger to sign his dies (so they could track the quality of the dies). For their button dies these did not have to be cylinders but more often cone shape. Thousands of these have survived with the diestock makers name stamped on their sides.

Tool steel specially for die striking parallels the development of the steel industry. As needs of metalworkers were recognized, the steel industry prepared special tool steel to meet specific needs. Mints and medalmakers wanted a steel that could be easily softened (to be hubbed or engraved with the design) then hardened for long, hard used for striking the greatest quantity of pieces.

Die Trial.  An early strike during SETUP of a coin or medal press in which die alignment, pressure and rotation may not yet be perfect. A die trial usually lacks a depth of relief before the pressure is fully brought up (it looks like a worn coin) and is discarded before satisfactory setting of the press for a production run. Die trials during press set up are always done using production planchets.

Die trials are sometimes struck in lead or other soft metal blanks. This is done to verify that the die pair is complete and that metal flow is as expected.  Such soft metal die trials are similar to LEAD PROOFS (except they exhibit both sides, lead proofs are usually one-sided). Lead die trials usually show an imperfect die alignment and an extended FLASH (being struck in soft material without a restraining collar).

Die trials of coins -- setup.  Every time a press is setup a number of trial impressions are taken, adjustments are made until the pressman is satisfied that all is in perfect order. These press setup test piece are usually destroyed – but a few of these have reached circulation and into the hands of collectors.

Die trials of coins – design tests.  When a new design, modified design or new alloy is ready for use, a Mint will make a test run of the coins to make sure the dies perform as expected under planned working conditions. These coins are sometimes called “die trials” although they are better described as “production test pieces.” Production tests usually include several hundred thousand to a million pieces. If everything is satisfactory, the production test pieces might be delivered to the Cashier. This was done with low relief Peace dollars in February 1922.

The Royal Canadian mint has made small production runs of an EXPERIMENTAL PIECES or TEST COINS; testing innovative bimetal compositions.

Off metal blanks.  Blanks of base metal have also been used for precious metal coins and medals; thus bronze blanks have been widely used to test the dies intended for gold coins (rarely silver coins). While these pieces are highly prized by collectors, they have been called a number of different terms in addition to trial strikes:  die trial strikes or trial pieces, and since they are off metal, they are called OMC for off metal composition.

CLASS 06.4


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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