And what about the B behind bust and the gamma? What do they stand for?
Those are control marks and serve an internal function, like accountability. Without all these different marks, officials would not know who minted which coins, but control marks allowed them to know who was responsible; for example if coins came up lighter than allowed, meaning someone was perhaps shorting the coins and keeping some of the metal, they would know who minted the coins.
On the FTR, most of the busts have no letter behind them, but you will also find A, B, delta, epsilon and M. On the reverse, there are many different marks possible.
