<VV> Coil Heater

[Padgett]

While working on the idle this morning it was noticed that the coil was 
getting way hot (checked and is 5.8v at + term with engine stopped, points 
closed, and ignition on so assume resistor wire is in place).

When replacing with a "for use with ballast resistor" unit, it was noticed 
that there is a "D" shaped hole in the shroud directly under the coil.

1) is this a coil heater ?
2) is the edge of the coil supposed to fill the hole ?

Why is it there ? (Figured someone would know).

Padgett