Hi Bob,
This 20mm Oerlikon is a manual 1930's design that was license built in a number of nations prior to and during WW2, (even Japan). It was found to be ineffective against faster aircraft later in the war. It was still used up until the 1980's though. Oerlikon is still in business, producing various weapons. My model is 1980's design with heavier shell, higher rate of fire, and power elevation and traverse.
Hope this helps,
Dave