not a lot of fun to solder them up, but still used to this day for a reason: they work.
Their ordering system makes as much sense as a snow cone cart in the Arctic, but once you understand their language, you can usually find what you need.
These particular ones are recycled. Gold pin bayonet mount ones. I usually go for standard silver pin and standard threads. But these were free, and seemed up to the task of carrying +15, -15, 0V and an earth ground up from the power supply.