In the early years of the 20th Century, the firm continued to develop its exports. New overseas customers, particularly in Asia, were acquired through Gustave Fulbaum, an energetic representative based in Berlin. As a result of Fulbaum's extensive travels, Guimaraens & Co. secured customers in Rangoon, Penang, Singapore, Yokohama and Shanghai, as well as in Hungary and Russia.
The company also pursued its own contacts. The company's approach was to send samples and quotations to as many potential customers as possible in the expectation that some of them would result in business. By 1910 the company's ledgers were recording shipments to Dublin, Jerez, Copenhagen, Moscow, Teplitz, Pilsen, Budapest, Eger and Graz.
Business in Asia continued to develop. In Britain, Yates Bros & Co. in Manchester was one of Guimaraens & Co.'s most substantial and consistent customers, remaining so right up to World War II.
The First World War
Shipments continued during the years of World War I, with Frank Guimaraens based at the offices of M P Guimaraens & Son in London and his brother, George, as resident partner in Oporto. The war brought many challenges, such as the threat to shipping. In the autumn of 1915 the steamship 'The Douro' was sunk with a cargo of Fonseca Port consigned to Yates Bros. As the war progressed, German submarine attacks intensified causing sharp increases in the cost of shipping wines from Oporto to London.
In spite of these difficulties, Frank Guimaraens continued to build the company's outstanding reputation for Vintage Port, in which he took great pride. In 1916 the house was successfully offering Fonseca Vintages from 1892, 1896, 1900, 1904, 1908 and 1912. The firm was also able to supply a range of Fonseca Crusted Ports that were lying in bottle in its cellars. These were usually identified by bin number, for example Bin 740, Bin 57 V and Bin 82 VG. This custom is recalled today in Fonseca's celebrated reserve blend, Bin No 27.
Another successful product was Fonseca's Choco Port, a very fine old wood-aged blend. Records of a 1916 delivery to Harrods department store shows that it fetched a higher price than many of the firm's Vintage Ports.