Holmes returned to Worcester and his electrotype business. They are both made of gilt copper electrotype. Relief printing encompasses type, stereotype, electrotype, and letterpress. Batteries did not have the electrical capacity needed to rapidly deposit the electrotype (or "electro"). After this, the block is dried and reproduced by the stereotype or the electrotype process. Like the 40 commemorative note, this note has an electrotype 50 in the watermark. In 1909 Holmes established his own Electroplating firm, the Holmes Electrotype Foundry. The first copies were electrotype printed at the Boston Stereotype Foundry. Nelson's Holyground recordings were released in February 2001 as "Electrotype". In 1879, Richard Worthington purchased the electrotype plates and began printing and marketing unauthorized copies. The electrotype was done by Elkington, Mason, & Co. for the Great Exhibition of 1851.