In 1981, a large number of 20 cent coins were required, far over the capacity of the Royal Australian Mint facility in Canberra, leading to some coins being minted by other Commonwealth Mints, such as the Royal Mint in London, and the Royal Canadian Mint. In Australian Coin Collecting circles, the Canadian impression of the 20 cent coin is known as the "Ottawa Mint" version, which may be misleading, as post 1976, the Ottawa Mint only produced precious metal commemorative coins, like the Perth Mint, meaning the coins may have been produced at the Royal Canadian Mint's Winnipeg facilities.
Due to differences in the milling and annealing process, the Canadian variety of the 1981-20 cent coin is distinctive to attentive collectors and even cash handlers. The top and bottom edges of the milling is rounded over, not squared like the Australian and London varieties, and despite being in circulation for well over 25 years, even when well worn, the fields remain shiny, and not dulled like those produced at other mints. These qualities are also observed in Canadian coinage of similar ages.
The quantity of 1981 and 1982 mintages of the 20 cent coin was sufficient to not require many coins released for circulation until 1990. The 1983 and 1984 versions were struck for circulation, but never released, later being resmelted by the Royal Australian Mint, leaving the coins relatively rare. Significant premiums have been paid for a small number of mint rolls from these years that have shown up in auctions.