I have built a clock using these. I love them. The mesh is finder on these than the IN-17, and B-4998's have pins instead of leads. 0-9 and anode, the two other pins might have been used in for the giver pill to release mercury vapor inside the tube. The round version of these in the Burroughs sub-miniature family are the 4021,4032, and 7977. The decoder and driver module is the BIP-9801-1 and contain an RTL 4 bit latch and BCD to decimal decoder as well as the anode resistor. Here is a picture of my B-4998 clock in the background with B-5870 nixies in the front:
And head on using NL-4998's (Same tube as B-4998, but I prefer the Burroughs) because the B-4998's never arrived yet.