Did you ever wonder when looking at a bimetalic coin how in the world did they ever attach the inner and outer metal alloys? when I asked some of my fellow dealers that question most did not know and I heard answers that ranged from friction to glue to microscopic strips of duct tape.(ha)

    A bimetallic coin or blank is produced from a disc-shaped core and an annular outer component. The metal alloy material of the core is relatively harder than the metal alloy material of the outer member. The two components are bonded to each other by pressure flow of the material of the core toward and into the inner edge of the outer member. According to the invention, the peripheral edge of the core is shaped or nosed such that it extends radially outwardly. During minting, the pressure of the dies causes the material of the core to flow radially outwardly, thus causing the shaped peripheral edge of the core to penetrate into the softer material of the outer member's inner edge and, thereby, form a tongue and groove connection which resists relative axial and rotational movement between the outer member and the core. The shaping of the core also facilitates the fast speed placement of the core into the ring during the minting operation. The invention is particularly, but not exclusively, useful in the production of thin coins having the thickness range of about 1.0 mm to about 1.5 mm, where the locking of the two components is difficult to achieve with known methods.

   I hope you will find this guide helpfull, thank you.