I found a source for the muster records and other military records for German soldiers in this war. Not all are immediately available to me. I was able to identify at least two dozen records for members of the families Hasselbacher, Bayerl, and Gnugesser. Records for cannoneers are not yet available. I await these anxiously. I have my grandfather’s WWI diary, but cannot tell where he fought before he was bombed from an airplane-perhaps a first in Sept 1914. You can see an introduction and some of the records here.
These military records have some basic family information including information about parents andd spouses. I think they will be useful to tie up some loose ends such as the Hasselbachers of Eschenbach and Markt Erlbach.
Addendum: The remainder of the records are now on-line including my grandfather’s. They tell exactly where and when he fought, where he was wounded, and what he did after.