In February 1907, the Royal Dutch Shell Group was created through the amalgamation of two rival companies: the Royal Dutch Petroleum Company of the Netherlands and the "Shell" Transport and Trading Company Ltd of the United Kingdom. It was a move largely driven by the need to compete globally with Standard Oil. The Royal Dutch Petroleum Company was a Dutch company founded in 1890 to develop an oilfield in Sumatra, and initially led by August Kessler, Hugo Loudon, and Henri Deterding. The "Shell" Transport and Trading Company (the quotation marks were part of the legal name) was a British company, founded in 1897 by Marcus Samuel, 1st Viscount Bearsted, and his brother Samuel Samuel. Their father had owned an antique company in Houndsditch, London, which expanded in 1833 to import and sell sea-shells, after which the company "Shell" took its name.

Answer this question, if possible (if impossible, reply "unanswerable"): When was the Samuel brothers' father's antique company created?
unanswerable