This is the tool to apply the Swarovski snaps and Decorative Buttons.
This tools was designed by Swarovski for simple, hand installation of the snaps and decorative buttons. Clothing manufacturers and other professionals use a "fly press" to install the snaps, which is thousands of dollars and takes up the floor space of a dishwasher. This handy gadget can't do 400 in an hour, but is way better for home use! You need a set of dies to use this - sold separately. Good video of it here.