Small scopes?
Even smaller: a pre-war W.&H. Seibert, Wetzlar, "Jaguar Sport 2x". Tube diameter 20 mm, length 19.4 cm = 7.6"

The smallest of them all: 1960s Hensoldt, Wetzlar, Diapi 1.5x7.5. Tube diam. 14 mm = .55", length 13.7 cm = 5.4"

This was a short-lived rule breaker, designed for small bore target shooting. The then German rules prohibited the use of scopes, but allowed elderly shooters to use "optical aiming aids", provided these did not exceed 2x magnification and certain dimensions. So Hensoldt designed this "non-scope" for cheating. Soon the rules were changed, hence these things are quite rare now.