Avon Knocking

This is a sweet little vintage lapel pin, which I guess may have been awarded to especially successful Avon Ladies. That dates me, doesn't it? But back then, it was all about your 'Avon Lady'. People of a certain age will remember only too well the adverts with the catchphrase of the doorbell - 'Ding Dong! Avon Calling!'.
So why is the lapel pin a door knocker?