Occasionally through the years a piano would arrive in the shop and when
we opened it up there would be a green powder all over the keybed and
keys.  I KNEW what it was, and taught my employees early on how to handle
it.  Now I am going to share it with you.

That "green powder" is...  "Paris Green" and I quote from Webster's on
this one"

"An insecticide and pigment prepared as a VERY (emphasis mine) poisonous
bright-green powder from arsenic trioxide and acetate of copper."

It was used to kill carpet beetles...  whom as you know...  live for
wool...  as in felt...  If you buy a piano, check it out before you bring
it into your house or shop.  We got a J & J Hopkinson Upright from
England with a very late Ampico A mech (lost motion pneumatics under
the keybed) and it was ALIVE with carpet beetles.  We had the movers
leave it on the sidewalk, covered it with a trap and fumigated it...
and the EPA...  if it had been in existence in those days...  would
have put me in jail for what we used to kill them!   Don't ask the
obvious...  the EPA laws may be retroactive.

Ed