Ammeter Strommesser Luftwaffe Fl32509-4

This is a WWII-era aircraft Ammeter (Strommesser) Fl 325509-4, as used in aircraft of the German Luftwaffe. 

It is 1 3/4" diameter, and 1 3/4" deep mounted in a black, steel cylinder by two small slotted screws. It has a movable pointer to indicate the current in an electrical circuit. There is a "0" above an "A" at center position flanked by a "L" and a "E" to the left and right of the scale, likely indicating negative or positive draw. stamped in white to the black mounting cylinder is "Anforderz. Fl32509-4" above "jjb". The ammeter could be illuminated from the back, as evidenced by a clear window that is visible when looking in from behind.