What I find interesting is the fact that there were several gunmakers that were somewhat dedicated to a family or crown. Like Wilhelm I and II I think also had dedicated makers and the W on their guns looked like W's. They probably had guns made from all sorts of German makers but obviously some were selected based on some reasons. The subject guns don't appear to be over the top ornate but more like go to everyday gun of a royal estate or for an owner that liked to hunt. Hard to say if they were gifts or not. My guess is that they were guns commissioned by the royal family for their own use, which that estate is now in Czech Republic.
Trying to figure out why a maybe somewhat dedicated Schwarzenberg gunmaker would make a gun with a W or M and not with an S. Going to the House of Schwarzenberg site that is below and going to era described the only guy in that mans world era was Johann blah, blah blah Maximin Schwarzenberg. My guess was maybe he went by Maximin, hence my M letter theory. I can't really see any names of people with Ws prominent in that so called 1860 to 1880 time frame. He would have been a teenager at that time in 1870's, which a matched pair of guns from the family gunmaker could have been a gift. Also go to link below and look at the crown used in sites wallpaper, it looks like a dead ringer for the crown on the gun. I think those are Max's guns since he was next in charge of the family affairs or maybe his wife's.
The other thought/hypothesis is that he married his wife Therese in 1889 when she was 19 years old (see below). She had a W in her last name. It was fashionable at the time for German women of means to shoot. Actually saw a sketch of a German Huntress in her fashionable attire and by her side was a SXS with a sling attached. 16 Gauge might have been suitable gauge of the fashion since this was age of Annie Oakley and I believe she toured Europe shooting her 16 gauge Parker, which might have been an influence. Guns could have been made earlier by the family gunsmith and given to her but then it might of had a TW in the engrave. I just don't know what was customary.
Also it appears that during this era when Johann and Therese were prominent that the Schwarzenburg family combined with his wife's Therese family holdings made them one of the largest landowners in Europe at the time up until the rise of Hitler and Nazi party. In essence if you were a large landowner at that time you probably either enjoyed hunting or at least had to look the part essentially if you were hosting hunting parties or events.
So only direct evidence we have is the guns with some engraving which popular opinion says is a W, and that the guns were made by the Schwarzenburg family gunsmith. As far as reasonable information that I have seen, the circumstantial evidence of that era points to one of these two prominent people as part of that family.
Here is link to Schwarzenberg Family site.
http://almanachdegotha.org/id101.html
2h) JOHANN Nepomuk Adolf Maria Hubert Maximin Fst zu Schwarzenberg (Vienna 29 May 1860-Vienna 1 Oct 1938); m.Vienna 27 Aug 1889 Therese Gfn von und zu Trauttmansdorff-Weinsberg (Oberwaltersdorf 9 Feb 1870-Neunkirchen 12 Aug 1945)