So these are current controlled thermal starters, pretty rare these days. These contain a heater element, what is heated by the current passing trough the lamp (or directly, or using an auxiliary winding on the ballast). This heat up the bimetal switch, what open, when heated up. This contact connect one pin from each tube side, while the tube is supplied from the ballast to remaining sides. So if you turn the power ON and everything is cold, the contact is ON and let the current flow only trough the lamp filament and heat it up. At the same time the heater heat up the bimetal, so after some time the contact open. This create an inductive kick, what ignite an arc in the lamp. If this was successful, the current continues to floe trough the lamp, so the heater is kept heated, so the contact remain open. If the ignition was not successful, the circuit current disappear, the heater and bimetal cool down, the contact close and the cycle repeat, till the lamp ignite successfully.
An option would be to replace the starter socket with the 2-pin one (store the original) and reconnect it accordingly. Other option would be to create an adaptor: Find a nonworking 4-pin starter, what have usable base plate, but the mechanism is not possible to repair (smashed, fully burned out heater,...). Figure out, where is connected the contact and connect there the new glowbottle starter rated for the tubes you are using there. At first try to connect there a mechanical switch, assemble the unit and try it with "manual" preheat (close the switch for 1..2second and then open it, after few trials the lamp should light). If you see no response (no glowing from the ends,...), try to connect the two remaining pins, where the heater was connected and repeat the test. In what setup the lamp light up, you keep that, only replace the mechanical switch with the glowbottle (regular 2 pin) starter.
But the question is, if it would not be better to keep everything original (to maintain it's historical value) and use some another fixture for the actual daily work, because these setups are very rare these days...
It is hard to explain in more specific way, as I do not know the exact configuration, you even didn't published, if you are from 230V/50Hz or 120V/60V region...
I guess many members here would really appreciate, if you would share some photos of it... :-)
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