I was watching Time Team last night " Life on the Edge 1,000 BC" a Bronze age site near the River Witham. http://www.channel4.com/history/timeteam/thisweek.html.
They found a strange piece of stone a couple of inches across with cup and ring markings joined by a tree structure of one cup and ring per branch. Sorry no photo. They interpreted this as a mould for casting cups and rings in bronze. So they produced small reversed cups and rings. That is a bobble surrounded by a raised ring.
I have seen Viking combs with the motif but nothing in metal.