How does this gas valve & lwco work?

Pretty old I have never seen a low water cutoff where the pilot gas?? is run through the lwco.

If it needs replacement it will be $$$

You could pm @Tim McElwain

pretty sure it is a modulating valve that uses gas pressure modulated by the boiler pressure to vary the firing rate.

I haven't seen one of these systems since about 1970. Most were a Detroit Lubricator Gas Valve, very expensive but dependable coupled with a safety system in which the flow of the gas is cut off if there is a low water condition in the boiler, an over pressure condition occurs, or the pilot itself goes out. The Gas valve also would modulate the gas flow based on steam pressure. These systems were safe until they were not. They were hard to service, adjust, and repair. I would say that, that system is probably from the 1950's. I doubt that any repair parts exist. If you are having problems or you want to make the boiler operate more safely get someone that can replace that whole control system; pilot, control,s gas valve, etc. As far as the boiler goes if is not leaking it could be utilized until it leaks which may be, never. That was a very good boiler and was made to last almost forever. One more thing, if the system is working let it alone. Unless you or someone else knows exactly what they are doing, don't touch it. If it breaks or quits working, replace it. If it were mine I would want a control system that is safer than what you have. One last item, I'll bet that the elevated train system gives you lots of enjoyable free time.