Steel Blue Square Corozo/Tagua "Five Squares Flat Pillow", 11/16"
Square button with four square holes. It's almost 1/8" thick but then slightly raised - 'pillowed' in the center, so it's not quite flat anymore. Steel blue-gray color. 9/16". $1.85 each. Satin finish, very smooth with a slight shine.
Vegetable Ivory/Tagua/Corozo: Click here or here for wikipedia articles about this tropical palm tree nut. Tagua has been used for buttons since the 1880's, before plastic. It is strong and durable, machine washable/dryable, with a unique texture that is much nicer than plastic.