This is a medium sized nixie tube of unknown model and manufacturer. Its a very old looking tube, and has maybe hand made or early machine-formed digits. It looks similar to the GN-1 manurfactured by STC. There where different versions of the GN-1, so my best guess is that this tube is a GN-1! Some of the digits are near the end of their life. UPDATE 11/JAN/2020 : I got a message about this tube, and it looks this is a GN-1 that is missing the usual black shrink tube which likely has fallen off over the years.