Hi I've been looking through my grandads tools and found an old spanner/ wrench. I can't identify the marking and was wondering if anyone had any idea what it says or if it was used for something special? Was thinking maybe it's wheelwrights

Unfortunately I don't know anything about this wrench, but it is a beast!

There  was a HARVEY Co. making  a wedge-adjust nut wrench for bridge, railway etc. construction well into the 20th Century.   The markings on this one don't look like they'd  be  HARVEY; the specialty tool companies sometimes were so closely connected to their customer base they could rely on direct communication & did not leave any print advertising behind.

2nd reply -- the more I study that photo the more I wonder if the tightening wedge should not be on the "back side" of the shank, similar to position of the tightening wedge in this 1890 catalog illustration.  If my surmise is correct, the jaw tips will extend the same distance, and the jaw faces will be closer to parallel.