Bag of 100 x 16mm (0.6 inch, or 5/8ths inch) Brooch Back, 5mm wide, 5mm thick, with a hook catch. Nickel plate.
Great unit to glue your small ideas on to. It can be used for a lapel Brooch, hat Brooch, a badge, medal, school Brooch, or club Pin, etc. Glue interesting things onto it like a little bit of wood, paint it and then glue feathers and beads around it, and resell them or give them away to friends.
Use epoxy glue for max strength, rough up the surface a little first with fine sand paper.