Hello:

I found and purchased a nameplate from "Machine Number 7800

                                                        The Marion Steam Shovel Co.

                                                         Marion, OH USA"

and at the extreme bottom right of the plate it says "K25"

Any thoughts you might have would be helpful and I'd sure like to know what it was bolted to originally.  I found it in a garden center near cincinnati and paid $37 for it.  I imagine it's authentic but I really don't know. 

The nameplate itself seems to be of cast steel and is approximately 24" long by 6" wide.