A 1875 Envelope Addressed to Sylk's Hotel

The Savoy Hotel has been in existence since 1841. It was built by H. Royal Dawson and was then called Dawson’s Hotel. It was built around the cottage called Woodwille which is now the Garden Cottage at the hotel. In 1868, the name of the hotel was changed to Sylk’s Hotel, and thereafter to Savoy Hotel. (See an envelope addressed to the Sylk’s Hotel above) The hotel was renovated in 2018 and is now part of Taj Hotels (Indian Hotels Company Limited)

  The bank was established in 1840 and was based in Bombay. Though, a commercial bank, it undertook certain functions of Central Bank as the Reserve Bank of India was not established at that time. It was merged with the two other Presidency Banks, the Bank of Calcutta and the Bank of Madras and was renamed Imperial Bank of India in 1921. In 1955 the merged entity was renamed the State Bank of India. Bank.

The Bank of Calcutta was founded in 1806 and was renamed Bank of Bengal in 1809.

The bank was risk averse and limited lending to a period of three months, leading to launch of other banks, many of which failed. The Bank of Calcutta, and the two other Presidency banks i.e., the Bank of Bombay and the Bank of Madras amalgamated in 1921 to form the Imperial Bank of India. In 1955 the merged entity was renamed as the State Bank of India. 

The sender of the 1905 envelope is National Bank of India. Read here about the National Bank of India

https://en.wikipedia.org/wiki/Bank_of_Calcutta

Mercantile Bank of India was founded in Bombay in 1853 as the Mercantile Bank of Bombay by Cowanjee Nanabhoy and Edwin Heycock. In 1858 the bank was renamed as Mercantile Bank of India, London, and China with a shift of headquarters to London and in 1893 was again renamed as Mercantile Bank of India.

The bank issued banknotes in Hong Kong, Singapore and Penang. It issued banknotes in Hong Kong from 1859 to 1892 and from 1912 to 1974. The bank was acquired in 1959 by The Hong Kong and Shanghai Banking Corporation and rechristened as Mercantile Bank Ltd. 

The current Headquarters of HSBC Bank in India is housed in the erstwhile offices of Mercantile Bank. However, the banking operations of Mercantile Bank were sold to Citibank who in-turn sold them to the Bank of Tokyo Mitsubishi.