
I am reasonably certain the circular item with the hex head insert is what we would call a "freeze plug" which goes in the side of a water-cooled engine... they're very evident on DB601s and 605s, and I believe may be found on Jumo 211s and 213s, but am not 100% certain on that. All I feel confident in saying is that it appears to be an airframe with a liquid cooled engine and at least one MG 131 mounted; candidate aircraft would include the Bf 109G-6 if it is known to be single engined, and Me 110, Me 210, Me 410 and Ju 88 if it's multi-engined.
Lynn