The Z562M2 is a special nixie tube manufactured by WF / RFT. It was made for german elevators and can display numbers 1 to 8 and letters E and K. The numbers are used for the floors, E is for "Erdgeschosss" (Ground floor) and K is for "Keller" (Basement, -1, U). There is also another tube, the ZM562M3, that can indicate two arrows for "going up" or "going down". A Z562M1 also exists, but this was not made for elevators, it can display X,Y,Z,R symbols for coordinates. This tube is very rare, i believe not many of them were made at all.