I may have answered my own question - of all places, Sphere Research's old archived website has this to say about IN12 sockets for sale:
*12+2 Pin Russian mil spec oval sockets, part number PL31a-p, designed for the Russian IN-12 Nixie, but also fit most oval pattern Burroughs and National numeric tubes, like the 8422, B-5991, B-59917A, KS-19944L1, etc. Sockets are marked with pin numbers (same format at the US tubes), solder tag contacts and have a molded in 2-hole mounting flange. The two center pins are simply clearance holes (pins 13 and 14), as they are unused on the IN-12, and rarely used on other tubes of this mechanical format. Slightly snugger fit than US sockets, but work great on both types of tubes.* *[image: IN12.jpg]* Sphere continues to be an asset even after they're gone ;-) -- 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 view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/d68d7d9d-46de-4706-a326-850578411aean%40googlegroups.com.
