Mid to late 19th century would be my guess, based on the blade shape (ricasso). The acorn drag on the scabbard is, as you mention, similar to the Horstmann and other scabbards associated with German origin and I wouldn't rule that out. Look very closely at the base of the blade for a crowned king or walking bear. There may also be traces of the retailer etch on the other side. While one page lists the type as early as the 18th century, I have my doubts. Certainly not this example. A similar crossed bones hilt motif but with a roman centurion helmet pommel appears later associated with American Scottish Rite lodges.
Both the Crowned king and walking bear are associated with the Weyersburg families/brothers. The walking bear mark is after the Wyersburg, Kirschbaum & Co amalgamation/merger.
Wilkinson had some daggers of this form. German Masonic also had dagger examples.
Cheers
GC