Interesting - perhaps the railings are original. I will definitely have to research the Indiana Bridge Co.
I'm looking at this bridge and I actually think the railing is original. The plates on the ends of the girders mirror the ones that affix the railing along the top. Usually with afterthought additions they are fastened in a non-conforming method(they don't quite seem to mesh together).
Indiana Bridge Company was known to make some very functional, but otherwise unglamorous girder bridges. They would often, however, give the railings special treatments.
They may have considered this advertisement, much as plaques on a through truss, to help sell more spans. I don't know who the builder of this bridge was, but they may have been using some of the same practices.
The latice railings on this bridge appear to be much older then the current bridge. I suspect that there was a truss bridge at or near this location, and the railings were recycled. The stone wing walls at the west end of the bridge likely remain from an earlier bridge. I will try to upload pictures soon.