the neck pins are labeled on the board and that one's blank
people use the 10-pin/8-pin labels but both varieties only have 8 pins. they're just physically different shapes and the focus pins are in opposite corners between CR-23 and CR-31 lol
the bad monitor, was the signal header pin solder redone? typically the outermost pins take the most abuse from plugging/unplugging, the solder will become fractured. the bit of solder around the pin will be disconnected from the circuit in this case. it'll be a visible black circle where it cracked, I'm probably not alone in calling those halos. but if you're missing the sync connection it should be a blank screen. if the Screen pot on the flyback is turned way up you'll have retrace lines, I think that's supposed to show if there's no sync signal right?
I'm certain all Neotec monitors have LM1203 chips (or at least an equivalent), if that's bad then you won't have visible colors on the screen.
@zenomorp may know more. I'm not really in a monitor fixing mode right now as I don't do much of it anymore.