There is no mint that starts with a "B" - the only pennies minted in 1943 either had no mint or a D or S. And to answer the ? for the other person. it has to be steel cuz the official mint records indicate the production of no copper cents dated 1943
There are a few copper wheat pennies from 1943. They accidentally left some copper planchets in the mint when the were starting to make the steel pennies