Bullion Blunder. Metal incorrectly alloyed prior to being cast into ingots, milled and blanked. The formula for the precise alloy is compromised, and the wrong amount of metal is added during the mix. This is difficult to discern in struck pieces unless laboratory testing is done. Infrequently the color is slightly different, more often there is no difference. A light color streak, however, might indicate improper formulation; a dark streak would indicate a scarce bullion blunder where the slag from the melting of the bullion was not removed from the surface of the molten metal. This anomaly remains throughout all the processes of rolling, blanking, upsetting and coining to be evident on the struck coin. It would exhibit a dark, hard, gray to black streak of impurities on a coin's surface.

For the weight of a blank or coin there is a tolerance – a tiny deviation allowed

from legal specifications. While the composition is stated precisely in coin statues, there is generally no stated tolerance set for the alloy mix. In modern times copper alloys have been observed with as much as 20% error in their formulation, silver alloys by 5%. In ancient times, the compositions vary widely and is the subject of much laboratory testing and study. Again, these bullion blunders are not obvious (and are revealed only when testing is done on the coins in the laboratory).