Death head buttons were a subset of the Leek button (named for the English town of Leek). They consist of thread wrapped around a core of wood or bone.
Death Head button variants on the top row (l.to r.) are metallic, hand-dyed linen, wool, mohair, and silk.
Bottom row are metallic, silk and two-tone silk.
Another two-tone silk button (Actual size: 5/8")
Two-tone buttons in silk and metallic thread
For folks who REALLY love stripes!
Yet another pattern in silk.....
Some three-color patterns