I bought a jack to my E3 Bavaria, then I bought another one for my E9 74 thinking it was the same jack... I found out it was a different jack so I bought a E9 jack in Ebay Kleinanseigen, there and sent it to my sister in Germany (my sister doesn't open boxes so she sent me a box with more parts many months later). I received an E3 jack back too (seller sent me the wrong jack)... now I have 3 jacks for E3 so I thought I would modify one and make it an E9, talked to 3 E9 owners here and all 3 have E3 jacks... all 3 are 74 or 75 year...