[David Brown]

When Isaw this picture of a 109E, I immediately thought it was a 109E-7. The description below the photo indicated that it was a Bf109E-4/N of 1./JG 27 [Reference: German Aircraft of the Second World War, Smith & Kay, 1972, p.476]

Based on various reference books, I was under the impression the only difference between an E-4 and an E-7 was the drop tank which in this case can be clearly seen in the photograph. In fact, the Smith& Kay book mentioned this very distinction just above the photograph.

Is it possible that the aircraft in the photograph was modified with an external tank in the field and thereby kept it's E-4 designation?....or am I missing something?