a# just means its an alternate CRC. Probably a slightly different revision of the game (update to the game code because of game bugs or perhaps a switch to cheaper components inside the cart).
[!] means a CONFIRMED good dump, meaning that the dump is definitely good. Games that don't have a [!] may still be good dumps (as long as they are not marked bad), however they have not been confirmed yet.
_ _ - - = = Pr3tty F1y = = - - _ _