Hi Michael,
you are absolutely right about the description it is by no means a katzbalger degen or landsknecht degen. This type of sword belongs indeed to the German sword style of estoc.
As you definitely know as well they are produced in Graz, Judenberg and Passau. there are a number of examples preserved in the Grazer Zeughaus. also these type of estocs were carried by Austrian harquebusiers and Hungarian hussars on horseback. in the wars with the Turks.
about the date we disagree..................... why not
The closed 8 ring guard is a later development of the open 8 guard.
the later estocs also have an integral cap at the quillion block covering the ricasso to keep water out of the scabbard and sometimes also an octagonal guard plate.
I think that the estocs with closed ringguards and scabbard throats can be dated in the second half of the 16thC, Also the Giegh/Visser one
and the open 8 shaped quards with the caps in the first half of the 16thC.(similar as the developement of the katzbalger hilt in the 16thC)
lit:P.Krenn 1997 pp30-31
kind regards from Holland