The inherent 18 meter error in GPS could account for most of it, but
I think printing and measuring are the real culprits. I don't
dispute at all the 80 foot difference you measured on the map. In
fact, that looks close. Ditto on Topozone. But I never measured
that distance on either map. I simply noted the position (from
Topozone) of the USGS tri-point. In the field, we went to that zero-
point and then paced the distance to the witness monument. It was
135 feet plus or minus a couple. So the position of the monument on
the map may be faulty, or the GPS was inaccurate, etc., etc.

When I carefully measure 9 chains from the monument on Topozone or
the paper map, I end up in the river. It feels like this result is
within the error bars.