Most of the Hilger & Sons antiques that I have are woodworking center drills. However, Hilger and his sons, like many other tool manufacturers, made a number of different types of tools and equipment ranging from bit braces to straight razors. In this case, they also made scissors designed to cut the slot for a button.
As you can see in the above picture, there is a gap in the blades near the pivot screw that prevented fabric from being cut at that end. The plated brass set screw, depending on how high it was raised, prevented the scissors from closing fully, thus determining the length of the buttonhole slot that would be cut. These German made scissors measure 4-1/2″ overall and can cut a 1-1/16″ buttonhole. I purchased these scissors in eastern South Dakota, so they probably traveled west from one of the larger cities in the northeastern United States (such as New York or Philadelphia).