numismatic rare coins
The 1851 opening of the U.S. Assay Office was a boon to the San Francisco gold rush economy. Miners and merchants could deposit gold dust and receive fair value in the form of $50 gold pieces, which were also accepted at par by the U.S. Customs Office.
The Assay Office pieces effectively removed private gold coins from circulation. In 1849 and 1850, numerous private California mints such as Baldwin and the Miner's Bank produced gold pieces. These were proven underweight, and merchants and bankers refused to accept them except at a steep (and profitable) discount. The bankers then took the disparaged private gold coins to the Assay Office, which melted them into market-acceptable $50 "slugs."
numismatic rare coins
