Elizabeth, eldest child of King George VI, took the throne in 1953, and she still reigns today. During her time, she has seen many changes throughout the world - the fall of Communism, the breaking of the Berlin Wall, the end of the Cold War, etc. Importantly for us, she signed off our Constitution in 1982 when Prime Minister Trudeau helped Canada become a fully independent nation - still a member of the Commonwealth, though. The penny has gone through a number of changes over the past 50+ years. The first portrait of Queen Elizabeth II was of a young lady with a laurel wreath in her hair. The reverse featured a continuation of the maple twig introduced in 1937. The portrait of the Queen changed in 1965 with an updated model featuring a tiara in her hair. 1967 saw a one year replacement of the maple twig with a rock dove - commemorating the centennial of Confederation. In 1979, the tiara portrait was made smaller to make the size of the portrait proportional to the diameter of the coin (the same portrait was used on all Canadian denominations).
Funny story - in 1979, the mint tried to reduce the diameter of the cent to 16mm from 19.05mm. Unfortunately, it was the same size as the tokens used by the Toronto Transit Commission (the TTC), so the plan was scrapped. In 1980, they introduced a slightly smaller coin that was a bit lighter - 19mm instead of 19.05mm.