The Esso man key ring or key chain was first introduced in the 1950’s.  His head represented an oil drip. They became a big craze in the United Kingdom during the mid 60’s, especially amongst the Mods and Rockers, along with the Esso Tiger Tails.  Advertising at the time featured an Esso boy and girl character riding a scooter.  There were many different  styles designed by different countries. By the mid to late seventies they were virtually unavailable.  They have recently been revived though in Japan.