When Moses heads to the fair, he has "a deal box before him to bring home groceries in." Does anyone know if this is a wooden box made out of deal board (deal board is mentioned in MP, so that's why I'm making this connection)?

Then, Mr. Burchell gives the "little ones a pennyworth of gingerbread each, which my wife undertook to keep for them, and give them by letters at a time." What does "by letters at a time" mean?