6mm Tactile switch, square top. Manufacturer is unknown. They are through-hole PCB mount and will snap right into a solderless breadboard. Pin spacing is 0.3" x 0.2". Great for a reset switch or small keypad. Actuator measures 2.4mm square and rises about 4mm above the switch body. These were obviously designed for caps, but none are included.

There are 4 pins. 2 pins are bonded together on each side. All 4 are connected when the switch is pressed.