I believe the key here is number "F353" where F stands for F-Anlage / Funkanlage (Radio reciever / sender equipment) and next 3xx can indicate it be part of Fu Bl., what was blind beam (landing) or navigation system by Lorenz. Reciever antenna was under rear fuselage, but was flush on Ju 188 D-2 (Recce) version.. Part 9D of Ju 188 manual likely can solve this, but I can not find it my files, not shure I got it.
Above info is deducted from Manual "Part 9B Bordnetz" for Ju 88 A-1 / A-5 version, and does not go into deep parts detail.
Experts can correct this if they so whish...
I wonder if assembly F353 contained an light bulb, flashing if an Marker on the approach system was passed.
http://www.island-images.co.uk/ATC/z...orenz-diag.jpg
-Ed