Missing bass string

[Ted Simmons]

I tuned an Acrosonic spinet yesterday that had a bass string missing and it
wasn't stored at the bottom of the piano as is often found..  The owner
wanted a replacement and not a universal installed.  It's an older
Acrosonic and Baldwin doesn't have the scale for it so they sent what they
thought would work.  It didn't.  Does anyone have an accurate way to take
measurements to order a new string?  I don't want to remove the action and
I can't get a steel roll-up tape measure past the dampers.

Ted Simmons, Merritt Island, FL