Acid Treated Die
San Francisco Mint workers experimented with two types of acids (Nitric Acid and Sulfuric Acid) to fill in over polished areas of working dies. Both types of acid were used to refine bullion. Examples of acid treaded dies are the 1878-S VAM-49, 1878-S VAM-50, 1878-S VAM-76 and 1878-S VAM-81. The 1878-S VAM-36 has the most touch-up engraved and acid treatment in the entire Morgan Dollar series. Acid treated dies can also found in the 1879-S, 1880-S, 1881-S and 1882-S mint years.