What SU stands for

[Jon]

Not only did English cars stick with a color code across makes, the
colors actually meant something. White was directly from the "on"
position of the ign switch; black was for ground. So the coil had a
white wire for power, and a white with black trace for the wire to the
points, which of course is the low side switch for the ign circuit, ie,
the points ground the other side of the coil. To me, that was nice
logic.
TVR Jon