Commercial cover franked with a pair of Scott В186 commemorating the 50"' anniversary of Emil Behring's discovery of a serum for diphtheria. The special postmark was used at Leverkusen, and reads “Commemoration Festival in Marburg.”
It was in Marburg that the diphtheria antitoxin was first produced for commercial use. The postmark has a facsimile of Behring’s signature, and was used from 4 to 6 December 1940. Bayer AG, the German chemical and pharmaceutical company, was founded in 1863 by a chemical salesman, Friedrich Bayer (1825-80). It now operates plants in Germany and more than thirty other countries. Company headquarters have been in Leverkusen, north of Koln, since 1912. Bayer was in the I. G. Farben chemical industry cartel until it was dissolved by the Allies in 1945.
The company’s trademark, the Bayer cross, is internationally famous. Bayer was the first developer and marketer of aspirin (1899); of the first sulfa drug Prontosil (1935); and of polyurethane (1937), the base material for synthetic foams, paints, adhesives, fibers, and other goods. Bayer also developed heroin in 1898, but discarded it after learning of its addictive properties.