John is correct, that Steinway (and some other manufacturers as well),
added a little extra damper above the hammer in the lower treble to correct
some tof the after tones.

Some of the manufacturers also fashioned a longer damper that more
effectively damped the string. This of course would be the dampers right at
the scale division of the temperament going from the high bass to the lower
treble unisons.

The most effective way to improve the damping in an older instrument is to
replace the hardened damper felts (Reblitz's book explains how to do this)
and to regulate the damping mechanism to work as soon as the key is
released. Many times this requires spoon adjustment in small increments,
repeatedly testing the note as it's done.

I hope this helps you somewhat.

Best of Luck,
Dan Armstrong