From The Hindu Business Online
At the centre of it all was the rupee, which, since 1835, had been a silver coin containing one tola (0.375 troy ounces) of the metal of 91.67 per cent fineness. Besides being a token coin made of silver, it was freely convertible against the pound sterling at a fixed exchange rate of 1s 4d.
As India had the world’s largest economy from at least the year 1000AD into the late 17th century, Indian financial measurements were in used across the Indian sphere of influence, which spread over all of SE Asia via religion and trade. When the French introduced the metric system across their colonies in the early1800's - Vietnam, Laos, Cambodia and part of South China the 375 number was converted into grams. With 37.5 grams being referred to as a Mot Luong or simply a Luong, then from there decimal factions of a Luong such one tenth being 3.75g.
In French Indochina, the colonial administration standardised the tael (lạng) as 100 g, which is commonly used at food markets where many items typically weigh in the 100–900 g range. However, a different tael (called cây, lạng, or lượng) unit of 37.5 g is used for domestic transactions in gold. Real estate prices are often quoted in taels of gold rather than the local currency over concerns over monetary inflation.