IV18 Pin Identification

[Smiffy]

I have made up some driver PCBs for IV18s, using an Eagle part from the Adafruit library. (See attached, if Google hasn't eaten it.)

There is some confusion when every pinout I find shows 22 pins - but the actual tube only has 19. Are the pins I see in Dieter Waechter's datasheet marked 'not connected' in reality not actually there?

In an attempt to identify pin 1 - which appears to be at the bottom of the tube in relation to the display, I assumed that only pins 1 and 13 (heater) would show continuity. Pins 1 an 13 do not show continuity - pins 1 and 10 do, further reinforcing my suspicion that 'not connected'  is a rather confusing way of saying 'missing.'

If pins 6, 7, 8 are actually gaps 6, 7, 8 (I notice the pitch of the pins on the front of the tube are less than at the rear) then I think I may need to re-hash the part library, as putting pads/holes on a PCB with nothing to go in them is, well, confusing!

Or are there two variants of the IV18 - one with unconnected pins, one with no pins?

Then I have the fun figuring out how to get hardware SPI to send 20, not 24 bits to the MAX6921 :-) (I'll probably bit-bang it.)