Lighting coil Honda MB 50, MT 50

We have put our multimeter on this coil and we believe it consists of two coils. Coil 1: Unisolated thread with ring in the end is ground for one of the treads from yellow isolation. Coil 2: Black is ground for the other thread from yellow isolation. We have no good explanation to why it is built like this. It is only what we have gathered...