Gentlemen
This bulge under the fuselage is a cover of antenna for Peil (Peil from "peilen" not Pfeil) G IV for a FuG VIIa radio set.
It's something similar in destination like later used ZVG 16 direction finder device for FuG 16Z radio (with it's PR 16 loop antenna). Rarely seen on Emils (I recollect three or four machines with that) it was rather used on Stukas.
That mount for a 300 l. tank was different than ETC 500 (and other bomb racks) used on Emils "B". Bf 109 E-4/B could not carry the tank when with ETC 500/IXb.
If I could make a guess - it's rather E-7 or E-4 rebuilt to E-7 standard keepin' it's original W.Nr.
I'm interested more in technical aspects of o'nine and maybe I'am wrong with unit's equipment, but I remember information, that I./JG 27 was equipped with E-4/N in majority.
So - here comes the riddle - was it E-4/N's or E-4's updated with tank instalation but retained their Werknummern? Or just one of a few E-7 is photographed?
I'm preety confused too.