I just looked up the russian data sheets on Dieter Wächter's page - for the ITS-1B it's 5V as you mentioned, for the ITS-1A it's 4V. As Mr. Nixie's thyratron kit does not take any precautions for the ITS-1A I was also searching for the B type but was unable to find some at the time I was planning to order the kit. So finally I went for the A types and the clock is still working although the drivers use 5V supply voltage.
I ordered the prototypes of the updated Andrews ITS1A clock, and they will be on the way to me early next week. I'll do a test build, and then if that goes well, I'll happily give away the rest of the PCBs (I only got 5 pairs made). But first we'll have to wait to see if the design update is OK. I didn't put a lot of care into checking the boards, (a side effect of such cheap prototypes available nowadays), so it's sort of 50/50 if they will be OK first shot.
The ITS1B tubes arrived from Russia and they're new as described and came well packed wrapped in sets of two back to back in thin foam sheets. I've got 16 of them. The seller mentioned to me that having extras is a good idea because he said if you're not careful the wires can break off... I'm wondering if he was just pushing more tubes on me lol since I'm not that familiar with these although I'm doubtful of what he said.
Legs do fall off. I have a box of ITS1As and whenever I look in the bottom of the box, I find a few legs laying around. I've never worked out where they come from, I've yet to come across a tube where the leg is really broken off.
I have a feeling that more often or not, these "spares" are the snipped off legs that were still somehow attached.
That's a quite a lot of spares you got there though.
The next thing I would do is test them. Do the plasma-globe test on them, and then check for shorts between any of the pins. Any pin to any pin should be open circuit to a continuity check. I had a nightmare with one: it had a short between pin4 and pin 14. The leads are so short because I had to take it off the board and then clean up the holes enough to allow a new tube to take its place.
I checked the rest of the stock and found that I had one other tube (out of about 100) with this problem.