.75" button from 1915, the fourth year of serials, made with seldom-seen process. Beneath the celluloid the area of the ship is covered in interior gold foil. The area of the ocean waters are in green foil. Upper part of the button is standard black text on dark blue paper representing the sky. The use of interior foils to create reflections was a process known as Crystoglas used by maker Whitehead & Hoag. Button is Exc. although backpaper is tanned with small flake gone.