Ancient painted words on Freeman Street near West say “Pierce Steam” something. I’d say it was likely Pierce Steam Heating, founded by John B. Pierce and Joseph Bond in 1881. By 1892 it had merged with two other companies to form American Radiator, so if this sign refers to Pierce Steam Heating, it — and the building it appears on — are no younger than from 1892. For the most part it’s holding up well.
[The building may not be quite that old; see Comments]