buttonmold

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A piece of wood, plastic, or metal that is covered with fabric to form a button.

from The Century Dictionary.

• noun A disk of bone, wood, or metal, to be covered with fabric to form a button.

from the GNU version of the Collaborative International Dictionary of English.

• noun A disk of bone, wood, or other material, which is made into a button by covering it with cloth.
• noun joints of encrinites. See Encrinite.