The Liebig Company, a producer of meat extract pastes and bouillon cubes, began producing advertisement cards in 1872. The average size of the Liebig cards were 110 mm x 80 mm, larger than the popular cigarette cards of the time. The cards were produced using chromolithographic printing techniques until approximately 1940, but the company continued to produce cards until 1974. The highly collectible cards were first given to customers over the counter, but later the cards, often produced in themed sets of six, were given to customers in exchange for coupons that the customers cut out from the product wrappers.
The cards were issued throughout Europe and often in multiple languages, including French, Dutch, German, Hungarian, Italian, and Flemish. It is estimated that there were over 11,000 different Liebig cards produced with the total number of sets exceeding 1850.
Petroleum-themed Liebig cards include one or more cards in the following sets: The Earth’s Treasures (1900), In the Caucasus (1908), A Journey through the Caucasus (1920), The Story/History of Gas (1921), The Production of Petroleum (1934), Exploitation of Methane (1955), and The History of Roumania (1960).
(Six examples from different sets shown above; J.Spencer collection)
Rickards, Maurice, Encyclopedia of Ephemera, 2000, Routledge, NY, 402 pp.
Petroleum History 
Love these cards. Thanks for sharing.
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