When Hong Kong was established as a free trading port in 1841[2] there was no local currency in everyday circulation. Foreign currencies such as Indian rupees, Spanish and Mexican 8 reales, and Chinese cash coins circulated. Since 1825, it had been the policy of the British government to introduce sterling silver coinage to all of its colonies, and to this end, in 1845, the Spanish and Mexican 8 reales coins were set at a legal tender value of 4 shillings 2 pence sterling. But just as in the case of the British North American colonies, the attempts to introduce the sterling coinage failed to overcome the strong local adherence to the silver Spanish dollar system.
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By 1858, London gave up all attempts to influence the currency situation in Canada, and, by the 1860s, it came to the same realisation in Hong Kong: that there was no point in trying to displace an already existing currency system. In 1863, the Royal Mint in London began issuing special subsidiary coinage for use in Hong Kong within the dollar system. In 1866, a local mint was established at Sugar Street in Causeway Bay on Hong Kong Island for the purpose of minting Hong Kong silver dollar and half dollar coins of the same value and similar likeness to their Mexican counterparts.
Reference:The History of the United States Silver Dollar
The tradition of the so-called 「crown」 size coin dates from the late 15th century when significant silver finds in Germany and central Europe were struck into talers. The word taler has been translated into many languages where the crown size silver coin has been used. Among these translations are daler, daalder and dollar.
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Spain issued crown size silver coins in the denomination of 8 reales. Spanish colonial American Mints struck silver mined in Central and South America into 8 reales and smaller denominations, most of the coins shipped back to Spain. The 8-reales coins not exported to Spain were used in local commerce in the New World, some of them eventually arriving in the English colonies along the Atlantic coast.
