7/8" with W&H backpaper used only in 1900-1901. Sealed under the celluloid against a cream paper background is a wet fly tied on a snelled hook, no eye. Our thanks to Mel Campbell who consulted additional fishing expert friends with the resulting consensus opinion that this is a March Brown, and old English pattern that made its way to the U.S. Button has trivial bit of gray age tone on the cream background. Early buttons with actual object sealed under the celluloid are exceedingly rare. We've also seen one 1890's stamp and one 1890's Indian Head penny sealed under the celluloid but this fishing fly is most unusual and unique in our experience. VF.