[ Bob Stewart asked in 090412 MMDigest:

> Anybody have any ideas how mercury would find it's way into
> a pedal regulator?

Possibly the mercury came from an early version of a mercury vacuum
gauge.  The first vacuum gauges were water column.  If the vacuum
became too strong it could suck the water right up and into the piano.
Perhaps this occurred with a mercury gauge?

In addition, I have never encountered a model B upright.  It must be
very rare.

Bruce Clark