There were three manufacturers of the ZF4 scope, ddx, dow and bzz. There are several small changes to these scopes and slight variations to their markings. Carl Zeiss also made a version of the scope known as the ZF K 43/1
Example of a ZF4 scope with the gas plug added. These plugs were add so that during production the scope's o-ring seals could be pressured tested followed by vacuuming out any moisture. Once this was done a nitrogen dry air was sealed inside the scope via the plug.
Early ddx scopes have a small screw on the ocular of the scope. This screw was used to secure and center the internal lens mount and to protect it from recoil. These are not found on later scopes.
Example of a ZF scope with a large thread objective lens. It is not clear why these were made.
Example of a L marked scope for use with the FG42 by the Luftwaffe
Example of a P marked scope. Possibly for use with the MP43.
Example of a Bu marked scope which seems to relate to the retilce.
Carl Zeiss ZFK 43/1 Scope
Examples of ZF K43 mark on QVE 45 Rifles