This is a set of tools, called dice shapers, used in the production of beveled dice. This particular set of dice shapers is of great historic significance because it came from the warehouse of Hunt & Co - one of the leading crooked gambling suppliers of the early to mid 20th century.
Beveled dice are a type of crooked dice with beveled sides. As the name suggests, some of the sides of the dice are beveled, instead of being flat. When the dice roll, they are likely to roll off a beveled side and come to a stop on a flat side. In fact, expert dice mechanics swear that beveled dice yield a far better percentage then the more popular loaded dice.
The way that dice shapers are used is more or less self-explanatory form the photo. Basically, one must first lay a piece of fine-grit sandpaper into the well of the dice shaper, and then slide the side of the cube across the surface. The three different shapes produce strong, medium, or light work. Also, smaller dice are usually shaped in the deeper wells.
These three dice shapers were used fro decades by Hunt & Co and finally retired in 1961 when the company stopped distributing crooked gambling supplies.