Stone re-use in a modern "defensive" wall

On ancient and medieval sites you frequently run across older stones recycled into new construction. If you are a worker on anything other than a high profile palace or some such you are just going to use the stone that is easily at hand.  Hmm....lets pull a few off that tumbled down structure over there....

Often this results in the preservation of inscriptions that would otherwise be lost.  Particularly in the late Roman and post Roman era the builders probably had no clue what those scratchy lines on the stones even meant.

I have run across a few such stones when excavating at Vindolanda.  But it was a bit of a surprise to find the same thing going on with the flood control wall around a local creek.  Explanation at the end of the post.

A picturesque view on a very chilly day.

A real hodge-podge of material in this wall.  Polished granite for instance.

Closer to an explanation.  This slab has a depressed area chiseled out.  It looks as if some sort of plaque would have been mounted there.

Hiding under a flow of ice we find a date from the late 1800s.  The flood control wall seems to have been built in the 1920's or so.  The workers used whatever was at hand including left overs from a monument company that had gone out of business.  As the above tombstone has a birth date but no death date one wonders what happened.  Did the sick person unexpectedly rally and recover?  Did the carver screw up and get the first line wrong?  Did the company go out of business on the day this was being worked on?

Way down near ground level is a final tiny enigma.  Not a formal grave stone carving of course, but is it a very inconveniently placed bit of graffiti?  Or perhaps a workers mark from the monument company?