[Healeys] Starter motor question

[john spaur]

When I took apart the starter motor to clean and rebuild it there 
were two bands on the upper part of the armature; the part at the 
opposite end from the commuter.

One band appears to be fiber and was broken. The other band is 
metallic but not magnetic; probably aluminum.

Does anyone know what the purpose of these bands are?

I know; another difficult questions. Extra points will be awarded to 
the person or persons that answer this question.

John
'62 BT7