You are right Adam, the parts matching condition wise...
The mustache could well be an replacement, but it’s hard to spot, because on this kind of masks (probably Haruta school), the hair was attached with lacquer to the body of the mask rather then through drilled holes. On the other hand, that would cost something and makes no sense, considering the general condition of the menpo.
In terms of the gusari-tare, I think the right way to fasten it to a mask, is shown in the picture from “aoi”. But I’ve to go back to my books for confirmation. The chain mail might be “fusa-gusari” or “futaye-gusari”, pics are too blurry.....