Quick question as I'm cleaning the armature, and before I go to far.  I'm wondering what is under the commutator?  Like in this picture here:
http://www.delawareja.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=36689

or here:
http://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/24378330596072201/filePointer/24519132326113638/fodoid/24519132326113631/imageType/LARGE/inlineImage/true/IMG_1016.JPG

Is that crud and old grease, or is it some kind of padding that Lionel had put in? 
Kind of silly question but before I start digging it all out with a toothpick.. I've yet to find one in my google travels of a super clean mint armature!