While circulating San Francisco coins are no longer made they were once common. Your best chance of finding one in circulation is the cent. Nearly all wheat cent have an S mint mark version.
Here's the stats...
Type/Country: 1 Cent / United States
Metal: 95% Copper, 5% Tin and Zinc
Value: $0.10 in F-12
you have an older cent and want to know its value? Leave a
comment/question and I will do my best to find out the price and history