Diamonds were discovered in Brazil in 1725, and for the next hundred years the Portuguese monarchs derived great wealth from the country by establishing a royal right to every diamond weighing more than 20 carats. This right remained until Brazil claimed its independence in 1822. Among the large diamonds found during the early period of Brazilian diamond mining were two giants weighing 630 and 657 carats.
Theoretically it is possible, therefore, that this emerald-cut of 127.02 metric carats may have originated in Brazil. In addition, as has been asserted, the gem may at some point have been among the Portuguese Crown Jewels. If that is so then it must have been before 1910 when Porgugal became a republic and the last King, Manuel II, went into exile. It was not among the jewels that remained in Lisbon.
On the other hand Laurence Trashes in his book ( Harry Winston, The Ultimate Jeweller) states that no information has been uncovered to prove the diamond's ownership by the Portuguese kings. The 'Portuguese' is believed to have been recut to its present shape from a cushion-cut that weighed 150 carats: the rough stone is said to have been found in South Africa in 1912. This is possible because that year yeilded two large stones, both from Jagersfontein, that could have been manufactured to produce a gem of 150 carats.
According to Mr Krashes, the New York newspapers on 13th March 1928 reported the sale of an emerald-cut diamond to Peggy Hopkins Joyce, a lady given to the collection of rich husbands and large gems. In 1951 Harry Winston bought the diamond from her and then frequently displayed it in the United States in his Court of Jewels. In 1957 an international industrialist purchased the 'Portuguese' from him but five years later traded it back. In 1963 Mr Winston presented it to the Smithsonian Institution where it remains on display today. The diamond has been described as the 'unknown' among the great collection housed there, an epithet which it does not deserve because it is a very fine stone. Its shape is unusual: it has a nearly octagonal outline, the corners being almost the same length as the sides and ends.
The 'Portuguese' measures 32.75 by 29.65mm (1.29 by 1.17 inches) and is 16.01mm (0.62 inch) deep. In addition to its brilliant colour, the diamond has a slight milky flourescence that causes it to 'glow' even in artificial light.