I think you're right on the railroads.
The first row, stamps 2-5, with perfin "FNB", I believe are First National Bank of Boston.
The first pair of stamps on the second row is rather curious, as the perfin is in a different direction on each stamp. Nevertheless, the "BEC" perfin with the larger "E" in the center is Boston Edison Company.
Next to the last stamp on the second row "NSBK" is National Shawmut Bank (Boston, Mass.). See this previous thread posted on SCF:
https://goscf.com/t/11086