Seeking ID of strange "cheese grater" device on below cockpit window of some 1940 He111s

[Doug Stankey]

I do not know for a fact what exactly these are but I have a theory which is rather likely. These form an acoustic aperture that allows a public address speaker inside the aircraft to transmit sound to outside the plane. One can imagine a crewman yelling "clear chocks" or "stand clear" using this feature. The skin penetrations allow passage of the sound through the weather seal which is nothing more than a layer of doped cloth. Thanks to a clear closeup, I saw at some point I could see that the cloth has some texture and "pinked" edges (ie: zi-zagged) as done with pinking shears (just like my mother used to use!). Anyway we used something like this same arrangement to protect external speakers on our Bilevel passenger rail cars made at our local factory for Toronto.

I think that this is the most likely explanation.

DGS