The knurl on the contact is for additional mechanical retention only – it will need soldering for a true gas-tight joint. The contact is simply pressed into the PCB, with a bench press or similar.

Voltage rating is calculated from the flashover voltage – the voltage at which the electricity can break down the air gap and jump between two contacts. With a single contact, the voltage rating you achieve will depend on the space you leave between two contacts, or a contact and any other conducting element. So we are unable to give a voltage rating for single contacts, as it will depend on your usage.