I have a drawing of the fuel system of a 109 G-12 from the book "Messerschmitt 109 F, G & K series" of Prien and Rodeike (page 144), where these parts are shown at the front part of the cockpit below the cockpit floor, one on each side.
You can find a picture of these parts at
http://www.warbird.at/market/img_mar...nzinfilter.htm
BTW, a "Brandhahn" is a device to cut off the fuel running from the fuel tank to the engine in case of emergency or sometimes to simply cut off the engine from running. A fuel valve, if you like (I don't know the exact translation). So my guess would be, that a "Filterbrandhahnarmatur" is something like a combined fuel filter and a fuel valve.
Hope this helps
Robert