That spark lighter sounds somewhat like the RM-23 I have in my 1973 Hunter.
In that case the lighter knob is in the lower left corner of the inside of the refrigerator
. If there is a 1/4" hole in the back corner it means that the spark lighter iis missing.
However, that cover over the lighting
port looks home made and I suspect that the flint lighter broke or otherwise stopped working and a P.O. added the lighting
hole as a result. (As have I)
You wil also have to learn how to hold the pilot safety device ON while lighting. It's the blue looking button to the right of the gas valve temp knob.
Bigger question... does it work on electric? If you try running it on 120VAC and the boiler gets warm, but the box doesn't start getting cold after a few hours, there's little sense in worring about the gas function. At that age many, if not most, have gone to the great freezer box in the sky.