Originally Posted by apropos
Thanks again for your help mate, I suppose I can reciprocate here.
Horn - shine a light onto the button at an angle, you will see surface markings (may be very subtle). Will feel cooler against your face than plastic. Every button will be different. Less commonly polished, more commonly matte finish.
Corozo - from a Brazilian nut. will look perfectly flat at first, but a closer inspection reveals a fine grain,...