MOre I look at that I'd say that disc is from a plug hole. they some times have the central hole where a screw goes in.Now its time to build all in the mask that must be under the fabric.First the dynodes.
Cutted the dynodes arms..the best way is to use a scissors..a dremel makes the metal too hot..:
http://up.picr.de/25531915fr.jpg
The mouthkeys:
http://up.picr.de/25531954tx.jpg
The disc on the top:
http://up.picr.de/25532024la.jpg