I agree with Frank, it would be worth asking about the stem. You might point out the uniform, too.
FWIW, I found an image of Austro-Hungarian cavalry in 1898. Looks like they wore kepis, too! Their rank insignia is near the cuff.
http://en.wikipedia.org/wiki/File:KuK_Kavallerie_1898.jpgI didn't pay much attention to the blob above the hat. It seems too ill-defined to look intentional. The ambiguous shape of the hat, and the fact that armies of multiple countries wore similar styles, suggest that it's not a very good detail for ID purposes. The shape and placement of the chevron and the X on the hat seem more relevant. The suggestion of consulting someone who knows about these things is a good one.
Without meaning any disrespect of von Spaeth's opinion, I would still send photos to CMOG simply because if this does happen to be American and depicting a US Civil War soldier it could be worth a lot of money and have significant historical value.
I suspect "Americo-Bohemian" glass is more common in the US than people are aware of, but proving a piece is American it is another matter. "An illustrated Boston and Sandwich catalogue of 1870-1875, as well as quantities of fragments excavated at the factory site, shows that Bohemian-style glass accounted for a significant percentage of its production in the 1860s and 1870s." (
American Glass 1760-1930) A third of the glass shown by New England Glass Co. at a 1953 exhibition in New York was Bohemian-style. People today understandably assume such pieces are Bohemian.
For those interested in the subject, here's an article about glass by one of the best known engravers of this style who worked in America, the German-born Louis Vaupel:
http://www.cutglass.org/articles/art142.htmAlso a photo of a sample of Americo-Bohemian glass at CMOG. The goblets are New England Glass Co. (probably by Vaupel), and the pitcher is by Henry Barnes Leighton, son of the New England factory superintendent.