Hey Max,
Joe was not able to ID the Wappen on your helmet, even though he has an excellent book on Austro-Hungarian uniform. Sadly he loaned the book to another member, who has not returned it.
Looking through Joe's book, I can not find a good photo of the Wappen, except in the back of the book in the section on conservation, in that photo, the FJI Wappen is shown and captioned as an artillery crest, an donly the back is shown, but it is the style with the regimental number on the tail feathers like the one on your Frankenstein.
This is not an Austrian helmet (but then you know that) and the Wappen looks like it may have had been overpainted during the war, as the colour matches the example of an over painted Wappen in Joe's book. I would bet that you can find a nice Prussian Wappen to replace the Austrian one, and the Austrian Wappen is much rarer than the one that should be on your helmet.
Best wihses
Gus