From what research I've done, ivory was banned in 1925 due to elephants
being endangered and even though tusks can be removed humanely they
rarely were/are.

There are two parts to each key top: the head (front) and tail (between
the blacks).  Also, there are varying sizes, thicknesses, grains and
quality of ivory.  Even on a single piano the width of one 'D' may not
be the same as a second 'D' which makes replacement a tedious labor of
love.  Most heads have a bevel at the edge in front of black keys, so
a 'C' is usually not interchangeable with a 'F' or a 'B' with an 'E'.

To answer Larry Schuette's questions, Tom Strange of "Square Piano Tech"
has a great article:  http://www.squarepianotech.com/?page_id=274 

From "Square Piano Tech" you can click on the link within this article
for "International Piano Supply" or go to http://pianosupply.com/ 

Not to promote their business but is interesting just to research and
know a bit more about ivory.

Mid-page of "International Piano Supply" click "On-Line Catalogue
Orders".  Next page top left scroll down list in "Keyphrase Search"
to Ivory and takes you to "New Genuine Ivory Key Top Sets" cut from
pre-ban tusks in museums.  They also have salvaged used key tops, glue
wafers, and the clamps to apply them.

I found the above info in my two year quest to replace a chipped 'A'
head and some with small cracks.  Even though eBay does not allow the
sale of the "I" word, I bought some supposedly same measurement on
eBay without success.  I also got some non-matching from a piano shop.
I finally did find exact duplicates including the grain but a bit
darker for nine head replacements after my third try but it was from
a same vintage Chickering as mine.  I have not had the nerve to install
them yet.

As to white key tops: When my Weber arrived the keys were beautiful,
only slightly off white.  Not knowing better I left the lid closed two
years.  They turned nicotine orange-brown.  Leaving the lid up three
years they have lightened considerably from morning sunlight, but here
is the unusual note -- the ones on the bass end get more sunlight and
those are the darker.

As to celluloid key tops, the upright organ at my grandparents has been
in an unheated entryway forty-one years and the varnish/shellac is
jumping off.  The lid has always been closed, never played.  The keys
are also very orange, the treble end is right next to a window and also
darker.

My theory is that heat from sunlight on the lid does have an obvious
effect on celluloid or porous ivory from the gases of the old
stain/finish.  It also has a bleaching effect like lemon juice and
sunlight does on antique linens.

Some my Chickering's keys have red on the tails from the felt.  I have
been told commercial hair bleaching cream and #0000 steel wool will
speed up the process.  Any suggestions from others?

Best ragards, Linda Howson