As most smaller bikes in Germany in the late 50s, early 60s were 2-strokes, almost all gas stations had a pre-mix pump, mostly hand operated. The attendant filled a vertical cylinder with the amount of fuel you wanted and the unit mixed the appropriate amount of oil before dispensing it into the tank. We never knew what the actual ratio was. I assume it was the same for all bikes. Probably 1:25.
When we were kids, we ran around in the fields on old bikes the people did not want anymore. NSU Lux, NSU Max (4-stroke), DKWs, Zündapps and Horex. I still cringe thinking of that 350cc DKW and the Viktoria Bergmeister some friends had and beat up in the dirt.