I've bought a few of these and other similar types for just RMB 25 from China, the digit height is only 33mm, I had the datasheet translated by a friend, it says so at the end of the datasheet and I can confirm it from the tubes I have.
They are very fragile inside as the wires connecting the digits easily break from shaking during shipping, and while handling, and the wires also easily short against each other or the internal structures either killing some digits or letting two or more light at the same time - they are prototype quality and would need a lot more design to become good enough for serial production. It seems like the wires break due to being under strain and that the welding has punched through much of the wire making it snap easily. They are really quite poor quality for being "prototypes" even if they are rare. So I would definitely wait for the price to come down - I have enough for a clock and some spares but the poor quality has had me waiting to find more at a reasonable price! There are others with letters/texts inside, I have an SZ-3 (which has some broken wires) which shows the texts: Mn, Mo, P, S, Ni, C, Cr, Cu, Si & O (mine only shows Mn, P, S, Ni, Cu, Si & O) . I also have a much rarer (mega, ultra, super rare ;) ) prototype of the SZ-2, not marked, but with the digits made up from wires instead of from etched metal and no Anode shield and a rounder glass envelope, otherwise it is identical to the SZ-2, see photo below. These Nixies fit the Russian RSH-32 socket. <https://lh3.googleusercontent.com/--KP6PegBHsk/WqWF8c4Pg8I/AAAAAAAAB1M/eTfyTvOFAJ0n9OVVeGDEkEq7yZPVHmeaQCLcBGAs/s1600/SZ-3_compressed.jpg> /Martin -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to firstname.lastname@example.org. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/74a67e6e-ec3f-46e8-b2d7-527cc2f8c2bd%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.