To add a little to Keith and Willem's response, there is one sure way to tell ivory from plastic or celluloid. However, be cautioned that this is a destructive test...... Hold a small sliver of the material in a flame. Ivory will smell like burning hair; plastic like burning plastic; and celluloid will smell like burning fingers...(if you don't turn loose real quick!). Seriously, the celluloid burns very rapidly....don't use a large piece (and don't ask). If you are not adventurous, use a tweezer to hold the sliver.. Tom Robinson East Tennessee - making pianos sound better......one spinet at a time....
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