Pattye,
My research into MOP piano keys focused upon finding Exhibition grade (highest level) shells which could be cut into 6" pieces observing the maximum tolerances as provided by keytop specialists currently working with legal ivory, mammouth tusk, etc. It turns out this length would be impossible without complex lamination (even from P. Maxima), and cutting the notched shapes would result in nearly 100% breakage. However 4" lengths are certainly possible, making production of two-piece keytops (no notches!) more than feasible.
My research took me from Brasil to Korea to Broome, Australia (a smallish family pearler there), while developing sympathetic and unique sources. One European manufacturer of world-class grand pianos, Bl?thner in Leipzig, is seriously looking at offering MOP keytops on special order as a result of my request. They have researched the historical precedents (harpsichords from the 17th and 18th centuries) for additional justification.
So I am satisfied that something may eventually result, at the highest level of craftsmanship and tradition, from this exercise!
Steve
Seattle