The British Trade Dollar was a form of bullion coinage issued by the United Kingdom and intended to facilitate foreign trade in East Asia.
During the 19th century, the Mexican Dollar had replaced the Spanish Dollar as the chief coin in circulation in Asia. With the extension of British trading interests in the East, especially after the founding of Singapore in 1819 and Hong Kong in 1842, it became necessary to produce a special Dollar so as to remove the reliance of British colonies upon the various foreign coins then in circulation. As early as 1842 the suggestion had been made to issue a special Anglo-Chinese Dollar with value of 1,000 Cash, for general trade with China.
In 1845 copper coinage for the Straits Settlements was sanctioned by the East India Company, and in 1863 Hong Kong also obtained subsidiary silver and copper coinage, all based on the Dollar system.
These so-called "China trade silver dollars", issued much later, were a direct result of the First (1839 - 1842) and then Second Opium War (1856 - 1860), which broke out when Chinese authorities tried to stop Britain from smuggling opium into the country. The loser, China, had to open up a number of ports to British trade and residence, and cede Hong Kong to Britain. In the decades that followed, merchants and adventurers flocked to these areas, and international trade flourished. Foreign banks were established and large silver coins from all over the world began arriving to pay for tea, silk and Chinese porcelain to be shipped abroad. These .900 fine silver trade dollars were then circulated throughout China, where they were readily accepted as a medium of exchange. In 1866 a branch of the Royal Mint was established in Hong Kong and for the next two years struck dollars, half dollars and subsidiary coins. The Hong Kong Mint subsequently failed, but for a short while the Hong Kong dollar satisfied the need for a British trade dollar in the Straits Settlements and Hong Kong.
The years between 1875 and 1895 saw a rapid fall in the price of silver, which apart from disrupting trade also resulted in a serious shortage of minted dollars. To overcome this shortage, approval was given in 1894 for the minting of these British Trade Dollars, for general use in the Far East.
The coins were designed by designed by George William de Saulles and depict on their obverse a the figure of Britannia standing on shore, holding a trident in one hand and balancing a British shield in the other, with a merchant ship under full sail in the background; this is instead of the British monarch as would normally be the case on British coinage, in order to make them acceptable outside the British Empire. On the reverse is an arabesque design with the Chinese symbol for longevity in the centre, and the denomination in two languages - Chinese and Jawi Malay.
In 1895, the British Trade Dollar was given legal status in the British colonies of Straits Settlements, Hong Kong and Labuan. Its circulation in the Straits Settlements and Labuan was of short duration; after the Straits Settlements introduced their own Straits Dollar in 1903, the British Trade dollar was demonetised there in 1904 and 1905 respectively. It became exclusively a Hong Kong coin produced until 1935. Thus, it was known as a Hong Kong Dollar for most of its existence, and was only legal tender in that colony for most of the time; however, most coin catalogues list the coin type either under Great Britain or Malaysia.
The coins were for the most part struck in India, mainly by the Bombay Mint (with mint mark "B") and for three years only by the Calcutta Mint (with mint mark "C"); both were branches of the Royal Mint at the time. The Royal Mint itself also produced some coins in London between 1925 and 1930, with no mint mark. Coins with other dates which have no mint mark were struck in India, and the absence of a mint mark is due to worn dies. The mint mark "C" can be found in the ground between the left foot of Britannia and the base of the shield, while the mint mark "B" is located in the centre prong of the trident.
Note that mintages do not match how available or scarce a coin actually is, for a number of reasons. Prior to 1912, the accounting year of the Indian mints was from the 1st of April until the 31st March of the next year, so the mintages in their reports to not correspond exactly to the dates struck on the coins. The Royal Mint started striking coins dated 1925 and continued to use the same dies until they were replaced halfway through 1930. The 1921-B dollar was struck but never released for circulation, and only a limited number of 1934-B and 1935-B coins were released. A great many coins were melted in China.
In some cases, the date on an already manufactured coin die was altered. As this could not be done without leaving a trace of the former date, some coins show traces of an older date below the clearly visible date (so-called "overdate" varieties). Many of the genuine dollars are found with "chop marks" - small Chinese ideographic marks punched by local banks and counting houses to signify a coin was checked by them and they guarantee its authenticity. The practice was prohibited in Hong Kong and eventually fell into disuse. These marks are considered to not detract from the value of the coin; on the contrary - many collectors appreciate them as a piece of history.
The British Trade Dollar was finally demonetised in Hong Kong on 1 August 1937. | 
