Robert Bosch Z U 4
Bosch D U 4- duplex
the question is? What are these type mags fit?

Hello, the Bosch duplex mags not only say duplex on the base but they also have longer breaker point cams. The are used with a "VD coil". No- that is not a disease; it stands for vibrating duplex.
You with sometimes find these on early 'teens to twentys era cars , trucks and tractors. Aultman Taylor tractors, Reo cars and Garford trucks are where I have found them so far.
Combined with the air start pump, that makes the old Aultmans almost a self starter. The smaller engines like the cars and trucks sometimes get a "free start" if there is a charge of fuel in the cylinder, you just move the spark advance lever until you hear the buzz of the coil and if you are lucky they may just start without you having to crank!
Cheers- Michael