The Mercantile Bank Of India began as the Mercantile Bank of Bombay, taking the name of the city where it was founded in 1853. In 1854 the Bank opened an office in Shanghai and by 1857, it was granted a royal charter.
In 1857 the Bank established a presence in Hong Kong and later, changed its name to the Chartered Mercantile Bank of India, London & China. It moved its headquarters to London in 1858.
The Bank had branches across India, the Straits Settlements and Federated Malay States, in Hong Kong and in Shanghai. In 1893 it lost its charter and was reconstituted as the Mercantile Bank of India Ltd.
In 1959 the Mercantile Bank of India Ltd. was acquired by the Hongkong & Shanghai Banking Corporation. By then its name had been shortened again, to Mercantile Bank Ltd.
The acquired office in Bombay now houses HSBC Group’s Head Office in India. Mercantile Bank Ltd. was subsequently sold to Citibank in 1984 and to the Bank of Tokyo-Mitsubishi Ltd. in 1987.
M. B. I. overprints are most common on Foreign Bill stamps. I have only come across handstamped overprints on the King George VI issues. Overprints on postage stamps are harder to find.
Full name overprints were used on the first Foreign Bill stamps issued in 1855. The initials only C. M. B. I. L. & C. overprints also seem to be confined to the later issues of Queen Victoria Foreign Bill stamps. There are both horizontal and vertical overprint types, with a reverse version of the vertical style.