Steel tube housing with window cutout, using Mike Harrison's driver circuit to drive National Electronics NL-840 series nixies. This is a basic counter circuit that runs directly off of 115 VAC household power, and has "slow" and "fast" advance buttons for setting. The tall neon lamp in the middle, typically used for the number "1" on old Nixie meters, is covered in the center to make a colon. The colon flashes to mark seconds.