I have also this part, might have been cylinder shaped in it's young years.
http://imageshack.com/a/img842/4092/u8ln.jpg
http://imageshack.com/a/img62/8206/eo6f.jpg
Stamped on one side: "Franz Lange Berlin"
And on the other side: "Gerat Nr ?9-7015A-1 ??, Der Einsatz hat ??gene FI Nr, FI 32606-1"
It might be an engine accessory, or part of the cockpit instrumentation, I've looked all over the Ersatz-teil liste of the F and G, there are close Fi numbers, but stille no match.