>>1396344They're made of nixie tubes which use several filaments to display numbers. They were used in old computers before LED displays were a thing. They havent been manufactured since the 80s in the USSR though, so they can get expensive. Usually they use them for clocks these days and even watches, but these are a tool for time travel. You can put together a clock yourself if you can work with electronics a bit, otherwise a premade one will cost you a ton.
http://youtu.be/7qoxnkneIpA 