It gets more confusing because many piano manufacturers labeled their
upright pianos as "Upright Grand".  This, I was told, referred to the
stringing.  Before about 1850 (and much later in Europe) all pianos
were "straight strung".  That is, the bass strings didn't overlap the
treble strings.

Scale designers discovered the overlap idea, and moved the bass bridge
closer to the active part of the soundboard, improving the tone.  This
stringing was called the "grand" scale by some, hence the oxymoron
"upright grand".

I might also add that collectors refer to pre-cast-iron-plate
rectangular instruments as "square pianos", and the later monsters with
plates as "square grands".  The former had the annoying problem of
"racking" or twisting out of shape.  It's not uncommon that their lids
won't close when they're brought up to pitch!

Philip Jamison
West Chester, Pennsylvania