I have tried to get good pictures of these markings for a while and have tried all sorts of techniques. This method involved using a piece of my children's sidewalk chalk and rubbing it into the lettering, then gently wiping off the surface while trying to leave the chalk in the depressions of the markings.. This is the best method I have tried so far. I will keep trying to get better pictures, but this will have to do for now.
This one has: N.Y. STD, 139, 125. Very faintly on the lower left, you can see the ASME S stamp.
This is just below and has: 125, 110 HS, 1924, A.R.M.CO. The S stamp is in the upper left.
This next series of pictures is of the plate stampings that I found on the boiler barrel.
This one has: FLANGE, 55000 TS. (Really!)
This one just beneath the previous one and is: 11494, 45.
Underneath that is this marking. I have been unable to read it, but the bottom might say: CHICAGO ILL.