[Dekatron]

On early models AVO used different size on the hole in the collar, the side with the beveled hole is usually the larger hole (only by some tenths of a millimeter) and it is easier to push the pin out from the other end then (the side with the smaller hole) - later models have equal sized holes.

You can use a polygrip plier to compress and also to rotate the pin if it has seized up.

I usually put a tube, some 10-15 mm long, that fit on the pin on the side that I want it to be pushed out at and then use the polygrip plier on this tube and the pin to push it out into the tube far enough so that I can grip it and pull it out while rotating it slightly.