I recently watched a video of Nixie tubes being built and another user had asked what determines the stack order of the digits in front of the anode. I searched around trying to find the answer but I couldn't find anything other than several sites with a carbon-copy response that barely mentioned their ordering at all. Originally I assumed it might have something to do with visibility of each digit behind other digits but the order seems almost opposite to me if that were the case. Then I assumed it might have something to do with surface area of a digit and its distance to the anode but again the ordering didn't quite seem to make sense to me if that were the driving factor. Even the Wikipedia page itself shows examples of different stack orders in its pictures of tubes. So my question here is: What determines the order in which the digits are stacked in the Nixie tube assembly?
One such arrangement is 6 7 5 8 4 3 9 2 0 1 from front (6) to back (1). Russian NH-12A & NH-12B tubes use the number arrangement 1 6 2 7 5 0 4 9 8 3 from back to front, with the 5 being an upside down 2.