According to (my ignorance) Wikipedia:
The Hummer was a motorcycle model manufactured by Harley-Davidson from 1955 to 1959. However, the name 'Hummer' is now used generically to refer to all American-made single-cylinder two-stroke Harley-Davidson motorcycles manufactured from 1948 to 1966. These motorcycles were based on the DKW RT125 [DKW was the world's largest motorcycle manufacturer in the 1930s], the drawings for which were taken from east Germany as war reparations after World War II. RT125 drawings were also given to Britain and the Soviet Union as war reparations, resulting in the BSA Bantam and the MMZ M-1A Moskva, later known as the Minsk.
This cheeky tiddler is a 1954 Model 165(cc). BP