90.11 OZT silver pour bar. Unmarked, bar has old embossing labels U.S. MINT S. F. SILVER - 90.11 OZ and grease pencil writing 90 11 on underside. During the 1960's, silver certificates could be exchanged at US Assay office for their value in silver. For larger volumes of exchanges of certificates, silver bars were offered. With a large demand, these bars were poured quickly and in high volumes. San Francisco office was largely responsible for producing the larger bars. The bars were guaranteed to be at least 90% fine silver.