The following Q&A is excerpted from Clifford Mishler’s Coins: Questions & Answers
Q: I have noticed that Canada, the United States, and Newfoundland have all issued 20-cent coins at one time or another. Can you shed any light on why this coin ever came into being and why it was never accepted?
A: A 20-cent piece is a logical unit of a decimal coinage system; a 25-cent piece is an anomaly. However, the pre-national currency experience of both the United States and Canada was predominantly influenced by the Spanish dollar and its eight subdivisions, of which the two reales (two bits) had a value of 25 cents. It should be remembered that the Spanish dollar and its minor coins were legal tender in the United States until 1857, and that U.S. coins circulated freely in Canada before that country established its monetary system. Familiarity with the 25-cent denomination, and the desirability of maximum equivalence in the minor coins of concurrent currencies, established a use precedent for the quarter which a 20-cent piece was unable to replace in Canada, although the 20-cents denomination was readily accepted in more remote Newfoundland from 1865 to 1917, when the switch was made to the 25-cent denomination, likely due to the interchange of coins between Newfoundland and Canada, since Canada had produced the 20-cent pieces only with its initial coinage of 1858 and switched to a 25-cent denomination in 1870.