Loo, I don't remember seeing the button at the 8 o'clock position when I checked that watch at the MV gtg...
Excuse my ignorance but mind telling what is the function? 
Flyback.... resets the secondhand back to zero. So you can get synchronisation on the go.
The B-uhren are actually not for pilots...but for the "observers" aka the one who looks out for target and release the bombs. the pilots just fly the cargo to the drop zone and back.
thus if they have such a precision timing device last time...imagine the destruction it would cost 
I definitely give it to GO for such a simple and ingenious addition for an update to the traditional function og the B-Uhren.
The Germans are after all about function before form. 
I see... Thanks for the info... Sounds similar to to the Zenith Retrotimer...
well .. not quite. the Retrotimer just removes two modules namely the hour and second modules and is used as a 30 minute chrono. the central second hand would only engage when activated by the chrono pusher.
the GO Navigator instead is just a normal centre sweep second equipped with a flyback button to reset back to zero when engaged. Thus the primary function is for synchonisation.
Imagine a situation where... bombers are flying in formation to a target drop zone. minutes to target, radio command is relayed to all planes to reset the button and synchronise their watches; "drop at exactly 3 minutes from now" ..
So you can imagine the combined carpet bombing effect with such precision timing.....
