Base diagram shows it as some sort of triode. Using the wrong one is asking for an accident to happen. Make sure you know which is which. The AC rating is because they are motor-start units. They are used to provide an additional phase for two phase motors.
Some newer versions use a plastic film dielectric instead.
These are high quality capacitors that work well in power supplies at low frequencies. Do not expect these to work at RF, however. Their construction is a little more complicated than two conventional electrolytics in series- oposition but this is a convenient way of looking at them. They are not designed for DC operation and probably are best avoided as the reversed polarized capacitor can overheat. In fact, ALL non-polarized electrolytic capacitors are designed for intermittent use only or for circuits where the polarity may change occasionally during the life of the capacitor.