The following reference to GCS and the company Sykes, Schwabe and Co. has been found in a paper on the internet entitled 'The German Speaking Communbity in Hong Kong' by Carl T. Smith. Unfortunate;y Carl does not give a source for this information which as follows:

"Gustav Christian Schwabe is listed as a German residing at Canton in 1837. He had arrived from Calcutta in November 1836 and sailed for Manila in October 1837, The firm of Sykes, Schwabe and Co. which later became Boustead and Co. had its head office at Liverpool with overseas branches at Singapore, Manila and Canton. Mr. Schwabe was manager of the Liverpool office from 1845 to 1853. He then returned to China to head the firm of G. C. Schwabe and Co at Shanghai. This form was dissolved by a lapse of time in 1859 and was succeed by Bower Hanbury and Co., Shanghai."  (See Hanbury family below)

Also uncovered on the internet is this envelope showing Boustead Schwabe as fowarding agents. Edward Boustead arrived in Singapore in 1828 and established his firm, Boustead & Co., not long afterwards. He helped establish the Singapore Free Press (1835) and the Mercantile Advertiser. On January 1, 1864 the compnay became Boustead, Schwabe and Company but in 1867 the old name, Boustead and Company was reinstated.

The Hanburys were a prominent English Quakers family who were involved in a variety of mercantile and philanthropic activities, predominantly in the 19th century. Daniel Bell Hanbury was the son of Capel and Charlotte Bell Hanbury of Stanford Hill, north London. He entered Old Plough Court Pharmacy in 1808, under the sponsorship of his uncle, William Allen, and married Rachel Christy in 1824. Their son, Daniel, was also a pharmacologist, and became a partner in Allen & Hanbury's. Thomas Hanbury, the third son, began his career as a silk merchant in Shanghai, and in 1867 purchased an old villa at Mortola on the road to Ventimiglia in northern Italy. He pursued botanical research, and his gardens were visited by royalty. Thomas Hanbury was knighted in 1901 for his philanthropy.