Serial number range: 272001-3017750 (1935-1980, approx. 22,800 produced). Production by year: 1935: #272001-273000 (1,000 units); 1937: #416001-416500 (500 units); 1938: #472501-473000 (500 units); 1941: #571101-582200 (400 units); 1948: #677001-677500 (500 units); ... ; 1966: #2156301-2176700 (1,700 units); 1969: #2371801-2372300 (500 units); 1977: #2874101-2874200 (100 units); 1978: #2881601-2881700 (100 units); 1980: #3017651-3017750 (100 units)