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. See postal history of National Bank of India here and read about the bank here.

A 1945 letter from Bank of Bengal can be seen here.

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

The Oriental Gas Company was established on 13th February 1857 under The Oriental Gas Company Act No. 5 of 1857. The Company was originally registered in England under The Joint Stock Companies' Act, 1856", with limited liability, for erecting gasworks on land granted by the Government in the vicinity of the Town of Calcutta, and for preparation of apparatus and materials for the manufacture and supply of Gas. The Act also had provisions for extension of operations to other towns and places.

In 1858, the company commenced operations and people of Calcutta had access to coal gas, distributed by the company. At that time, these companies used to supply coal gas, primarily for commercial use. The company continued to distribute coal gas as a fuel for more than 100 years till the 70s. The actual production was done in plants at Rajabazar and Howrah.

After Independence, the British sold the company to an Indian company i.e., Jalan & Co. In late 1950s, due to frequent breakdowns of old machines the business was not viable and closed down. However, The Oriental Gas Company was nationalised in 1960 and was rechristened Oriental Gas Company's Undertaking and supply of coal gas was initiated from Durgapur. 

In the 1970s, the name was again changed to Greater Calcutta Gas Supply Corporation, and the company became a 100% state company of West Bengal Government. During 1990s, the Greater Calcutta Gas Supply Corporation Limited started getting coal gas from Dankuni Coal Complex, a subsidiary of Coal India Limited. 

In 2016, Petroleum and Natural Gas Regulatory Board authorized the company to develop, expand and operate a CGD network in the Kolkata Municipal Corporation region, and adjoining districts of Nadia, North & South 24-Parganas, Hooghly and Howrah. The company formed a JV with GAIL (India) Limited under the aegis of Bengal Gas Company Limited to supply gas to customers in the domestic, transport, and commercial sectors. 

https://timesofindia.indiatimes.com/city/kolkata/one-of-asias-oldest-gas-firms-shifts-address-from-park-st-to-narkeldanga/articleshow/109115738.cms

https://www.commonlii.org/in/legis/cen/num_act/ogc1857190/

https://indianexpress.com/article/cities/kolkata/west-bengal-ropes-in-150-yr-old-firm-to-supply-clean-and-green-cooking-gas-in-2-3-yrs-2926859/

https://gcgscl.org/profile.html

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. 

Note: Please see mail from Mercantile Bank of India Bombay and Delhi to Lloyd Triestino, a shipping company, in reference to shipping document; one on particular refers to bill of lading.