Starting in the 1960s, customers who filled their vehicle up with gasoline at a Shell Oil station in Canada would receive a free promotional medallion like this one. These medallions came in various themed series - to collect them all, you would need to keep going back to Shell Oil stations. In Canada, medallions were released to commemorate the Prime Ministers, the various provincial coats of arms and provincial flowers, the various provincial animals, and more.  The Prime Minister series were made out of zinc plated with a thin layer of brass. But, almost always, the brass layer is found missing, leaving nothing but zinc. Another common defect is a weak strike on Parliament Hill - the very high relief on the heads of the Prime Ministers led to less metal going towards the other side of the token.