I have heard of piano plates that held after being repaired, and twice
as many that did not.  I have replaced a piano plate and it is not an
easy task.  If you use an "identical" plate,  you will have to replace
the pinblock, since there is a 99% chance the tuning pin holes will be
off.  The best way is to transplant another strung back.

Lester is not a rare brand, so I would look for a similar strung back
from a Lester (or a sister brand) from the same era.  Don't overlook
non-player uprights that often had the same scale.  Count the scale,
and measure the strung back. also, measure the distance between the
scale breaks, as these tend to vary over production runs.

The main thing to remember is to get the striking point correct.  When
settling the action, use the top action bolts from the original piano,
and pay attention to the position the action bolts were bent.  There
will be small differences.  Be ready to reposition the dampers.

There has been some debate from the purists about replacing the strung
back; however, making a piano playable to me is the goal, whether the
serial number is correct or not.  On my Foster piano there was no way
to tell except the number on the back did not match the plate.  The
strung back was actually from a Marshall & Wendell piano and I simply
switched the name plate.  (Not all piano plates are made this way,
however.)  I also did this to a Hamilton Baldwin; both turned out
just fine.

Good luck,
Andy Taylor