Our RVT-136 rivets are steel, plated with a nice antique bronzey color. These are semi-tubular, intended to be set with a splash tool or splash anvil in your hand press. You can also flare the end of the tube with a nail set or pointed chisel.  Hollow tube extends 1/4″ inside, and the outside length of the shank is 3/4, so, take away 1/4″ and that leaves 1/2″ and that’s just about exactly the thickness of layers you ought to use these for.  Slightly domed head is 3/8″ in dia.
RVT-136, packs of 50 for $8 flat, USA shipping included.