the government's official standard pound weight that had been brought from the United Kingdom. According to a description of the 1948 meeting, silver coins selected for assay were first placed between steel rollers until the thickness was reduced to , and then were chopped into fine pieces and dissolved in nitric acid. The fineness of the silver in the coin could be determined by the amount of salt solution needed to precipitate all the silver in the liquid. Numismatist Francis Pessolano-Filos described the work of the Assay Commission: The commission operated under rules first adopted by the 1856 commission, and then passed down, year to year, and amendable by any Assay Commission, although in practice little change was made. Under the rules, the Director of the Mint called the assay commissioners to order, then introduced the federal judge who was an ex officio member, who presided over the meetings; if the judge was absent, the members elected a chairman. The chairman divided the members into the committees. If there had been a change of officers at a mint, commissioners examined coins from before and after. After the committees completed their work, the members re-assembled to report their findings and to vote on their report. Every Assay Commission passed the coinage that it was called upon to examine. If pieces varying from the standard were found, that was also noted; the 1885 Assay Commission reported the one substandard silver coin, which came from the Carson City Mint, but urged the president to take no action, noting that the coin was underweight by an amount too small to be measured by the scales at Carson City. Remains of coins used in the assay were melted by the Mint; those put aside for the Assay Commission that were not used were placed in circulation from Philadelphia, and were not marked or distinguished in any way. There were thousands of coins for the commission, of which only a few were assayed. Commissioners often purchased some of the remaining pieces as souvenirs, although commemorative coins could not be purchased if Congress had given the exclusive right to sell them to a sponsoring organization—they were instead destroyed. Commissioners Appointments of members of the public to the Assay Commission by the president are known to have been made as early as 1841; the final ones were made in 1976. Many early commissioners were chosen for their scientific