I would guess that the early ones were of some hard rubber plant mixture or a mixture of mica and some secretions from the ole shellac bug:
http://books.google.com/books?id=RJun1eW...bug&f=false

& H.E. Shepard, New Haven, Ct. - 1874
http://books.google.com/books?id=yq4KAQA...lac&f=false


Kind Regards,

Raimey