Tom: you are absolutely right about mail used in the helmet from the 16 & 17 pictures. The rings, which are joining the rest of the mail with the helmet, aren't original. Take a closer look at it, and you will see, that other rings are just as they should be, and they are much different from these above them. I don't know the story, but most probably is, this part of mailing was destroyed, and someone (I suppose just after the II WW) made a quick repair. It should be done better, but the time was very hard in Poland in those days, and many repairings and restorations were made cursorily. If you take a very close look you will probably see that they aren't attached properly.
It's a shame I still don't have a book "Uzbrojenie Tatarów" (Tartars armament) by Mr. Gutowski, so I can't be sure, but if my memory serves me well, it is described as Tartar's helmet from the 19th century...as far as I remember.
Regards!