(This was written before the last 5 replies appeared. I agree that Pfohl engraved in a similar style, but so did many others, including engravers working for companies in different countries. The
engraving style is definitely Bohemian, but that doesn't really signify much. As written in Wilson's
American Glass 1760-1930: "Attribution of Bohemian-style glass to specific glasshouses is difficult, for the style became virtually international. It is also difficult to date because it continued to be made well into the twentieth century.")
Kelli and I both remarked on the X on the cap. There's a crossed sword insignia shown in one of the links I posted that denotes cavalry (
http://www.ushist.com/victorian_hats.htm), but I just realized you have to click on "Union Hats - USA - Enlisted" under "Civil War" in the upper right to get to the page.
I would think given the detail shown that the insignia would be pretty significant.
I'm not sure about this, and I would appreciate others' input, but I don't remember seeing many Bohemian examples with tight red and white twists in the stem like that found here. I've seen a lot of other red threading, but it has been much looser (and earlier). And this is a minor detail, but scenic engraved Bohemian glass I've seen usually has nice, neat tufts of grass. Something like that could easily vary from engraver to engraver though.
Wish you could see the saddle. I've looked through my references and found many images of Bohemian engraved pieces with horses and riders. Most (all but one or two of a dozen) have four reins, and from what I can see they all have nosebands. Western-style bridles don't have nosebands, but maybe they (or something similar) are used in Europe, too?
Anyway, considering the evidence (including the fact that other Civil War memorabilia was sold by the same people), I'm sticking with my guess that it's American. You might try sending a few photos to the Corning Museum of Glass.
Kelli, thanks for the additional photos!