The right to strike coins of the Rosa Americana desgn was granted to William Wood under contract with the British King George I, whose image appears on the obverse. The coins were to be made of "Bath" Metal (75% copper, 24.7% zinc and .3 percent silver). The resulting alloy was dark brassy in color and the appearance of the coins today suggests the ratios were not always vigourously applied (some coins are more coppery in appearance, others more greenish-yellow). The coins were struck while hot and soft on a press that raised the upper die high in the air, then literally dropped it onto the planchet below.
The surfaces on Rosa Americana coins tend to come with light natural pitting, which seems to be a characteristice of the alloy, but they are also subject to post-striking corrosion. Thus, surface quality becomes an important factor in judging grade and value.
Mint State Undated Rosa Americana Twopences are quite scarce and none are known in Gem condition.
For complete variety information about ths interesting series, read Sydney Martin's book, "The Rosa Americana Coinage of William Wood."