Quince uses the expression “French crown” not to refer to a French coin, but to refer to the top of the head of an ordinary Frenchman. His statement that some Frenchmen have no hair refers to the fact that baldness is a symptom of syphilis, and to the belief that the supposedly promiscuous French brought this disfiguring sexually transmitted disease to England. Thus, if Bottom were to wear a "French-crown" wig – that is, one with no hair – he would be going on stage “barefaced."