What is the "promissory note"significance mlk talks about

The verb in the sentence is in what voice

Give two details about the social and economic climate of the 1930s. were these details noted in to kill a mockingbird

What is implied in this sentence from mark twain's "the £1,000,000 bank-note"? i was puzzled, and wanted to discuss the matter a little further, but they didn't; so i took my leave, feeling hurt and insulted to be made the butt of what was apparently some kind of a practical joke, and yet obliged to put up with it, not being in circumstances to resent affronts from rich and strong folk.