The GR10K is a medium-sized nixie tube made by the English company ETL. It is unusual (though not for ETL!) in not having an anode grid. The anode is mainly at the back, extending a little up the sides. This causes problems with the display of digits the further they are from the back of the tube. For these photographs I used digits either side of the display digit as additional anodes. In addition, the stated cathode current of 1.4mA is way too small to get this tube to light evenly.