B.A.K. Batterie, Wainoden Luftschiffplatz in WW1

[david.edbury]

Hello

I recently acquired a postal envelope from the Kaiserliche Marine based at Wainoden Luftschiffplatz in WW1 - 1915 I believe. I collect Zeppelin and historic (incl. military) airship mail. The note attached refers to a B.A.K. Batterie but I cannot find any explanation of what such a battery is/did or any reference to the gruppe 280 Osten shown on the rear. Would anyone be able to shed some light on this for me? Scans of the item are attached in case someone finds it of interest.

Many thanks, Dave