Found this also in my wardrobe:

The German Secret Strong Point. Must be from the late 70ies and from a japanese manufactor (EIDAI).

Scale 1:72 painted and brushed by myself about 30 years ago.

The set  included a PZIVG, 1x 88 gun, 1 Kübelwagen, 1 Schwimmwagen, 1 BMW R75 with sidecar, 1 AA 20mm Quad, 1 AA 37 mm, 1 AT 50 mm and a searchlight.