I finally got back to doing the research on this weapon and can now confirm that it is an 18th century Hessian hunting sword.
The letters etched into both sides of the blade stand for Wilhelm Landgraf zu Hesse. There were two Wilhelms who were both Landgrafs of Hesse: Wilhelm VIII (1751-1760), and Wilhelm IX (1785-1805), so the sword dates from one period or the other.
It is definitely a hunting sword, but other similar pieces having the same etching on the blade seem more hunt-oriented than mine, with deer foot finials, antler grips and hunting scenes, etc. I'm wondering if the lack of hunt-related adornment on mine suggests it was intended for use in the military, rather than as a true hunting weapon. Of particular note is the fact that the Hessian Jaeger Corps, which was allied with the British during the American War of Independence, apparently carried hirschfangers instead of hangers and bayonets, so my next angle of attack will be to contact a couple of museums in Kassel and environs to inquire further.
Judging from photos of other examples, the disc guard that projects perpendicularly from the hilt is not uncommon with these older Hessian hirschfangers.
