If you look carefully at the photo of all four tubes you can see that the one to the right has a different label than the other three, it also has a date code on that label which the other three are missing. My guess is that the three with the same label have another type of bakelite socket compared to the one on the right, maybe they changed the type of bakelite between these two different models.
The one on the right looks similar to the leapsecond photo as that one also has a date code. /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 [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/85a6b651-ecb5-4158-b4c9-49c99726dc4c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
