> If a circa 1880's grand piano with highly carved legs gets damaged
> and a new leg is manufactured (carved) to replace the damaged leg,
> is the piano still considered an antique?

My father used to tell the story of the fellow who owned Abe Lincoln's
axe.  Of course, over the years, it had had three new handles and two
new heads.

There's also a famous DC-3 airplane that is revered for its age.  There
is, however, but a single wing panel that remains of the original.

These two instances point up the problem.  Instinctively, I'd say that
your piano would certainly continue to be an antique: just about every
complex wooden antique has had something replaced in it over the last
hundred years.  And though I've never restored a player piano or any
other sort, I believe that such a restoration involves the replacement
of felts, tubing, the ever-mysterious pouch leather, and various other
rotted parts.  It's clear that these remain antiques.

Legally, I don't know.  My guess is that there's a definition based
on legal precedent somewhere, and the place to get that is to find
a lawyer or judge who is a player piano enthusiast and get him to do
the research.

There actually may be several definitions.  One might be based on the
instrument's stated value at, say, an auction.  Another might have been
used in a customs law case involving the importation of the piano.

If I had to guess, though, I'd say that the instrument could certainly
be described as an antique, but it would be best to mention that the
replacement had been made.  Perhaps a notation ("Leg replaced 2004")
glued and varnished over somewhere inside the case might make everyone
happy.

Mark Kinsler