the centres of Spanish-American dollars, creating the "holey dollar". The two pieces were each used as coins, with values of one shilling and five shillings. Units of account and rating systems Because of the variety of currencies that were used, two measures were needed for order and consistency in financial accounting: units of account and "ratings" system. By general agreement, all accounts were usually kept in one currency, and coins and bills from other systems were notionally converted to that system for bookkeeping purposes. That step required a generally accepted conversion system, or "rating" of other currencies, typically based on their weight and the value of the precious metal they contained. The colonies all initially used the British system of "Pounds, shillings and pence" as the unit of account, but there was variation in the rating system. Each colonial government established rating systems to value the wide variety of foreign currencies that came into use. The two most important rating systems were the Halifax rating and the York rating. The Halifax rating set the value of a Spanish dollar at five shillings. This value was actually six pence higher than the value of the Spanish dollar at that time. The higher rating was chosen to encourage the continued circulation of the Spanish dollar and to discourage people from melting the dollars down for their bullion value. The Halifax rating came into use shortly after the colony of Nova Scotia was established in 1749, and was confirmed by a statute of the Legislature of Nova Scotia in 1758. Although the British government disallowed the Nova Scotia legislation, the Halifax rating continued to be widely used in the Maritime colonies and eventually in Lower Canada. The York rating was named after New York, where it had been adopted during the colonial period. The York rating set the value of a Spanish dollar at eight shillings. The York rating was introduced in Upper Canada by United Empire Loyalists. Although Upper Canada formally adopted the Halifax rating by legislation in 1796, the York rating continued to be used, apparently up until the union of Upper and Lower Canada in the Province of Canada in 1841. Government treasury bills Colonial governments began to experiment in paper treasury bills, often when needed to finance government expenses. The first Canadian colony to do so was Prince Edward Island (at that time known as the Island of St.