Dear Robert,
This is a very interesting kabuto-menpô set that was designed, as mentioned already, by Noguchi Zesai.
The mask features the peg (otayori) under the lower lip, sparse (pointed) teeth, yadome, the nagashi no ana is probably round, and there is most certainly a cushion on the inside part of the chin.
The helmet has shinodare, soft-matal shiten-no-byô of otayori shape, attachments for wakidate, there is probably red felt under the mabizashi (visor).
As Joe mentioned just above, the most recent publication on the subject is written by Mr Robert Burawoy. But please note that there is now a much more recent (2017), corrected and updated version of his book with full colour pictures available here:
http://www.deboccard.com/fr/category/15262-Produit-9782913217379.html
(you can e-mail them as they understand English info@deboccard.com)
Congratulations on your find !
Paul