That's cool, I can't think of what would make it bowl-shaped.
I once received at GameStore a quarter that looked like it had been run over by a train (it probably had, although the perp likely did it on the Green Line where it's easy to get to the actual tracks). The thing was stretched and flattened; both faces were very slightly visible still and the milled edge was more like a scalloped edge. Boss went
, wrote it off and I swiped it later.