Logic

An archaeologist unearths a coin bearing the inscription "57BC". How does he instantly know that it's a forgery?

related riddles

A man wants to buy a used car. He finds a beautiful Buick for $9500, but he buys it without paying a dime. How did he manage this?

What can you fill a room with that takes up no space?

What man can shave 10 times a day and still have a beard?