I thought that about the reverse, but it’s not consistent with the obverse, which made me doubt a full cast, though the sheet itself could’ve been poured and the reverse contact with a cold surface could potentially create the bubbles, before then being cut up and hammered from a clearly crude die?
Now here’s a question...would it ever have happened that cut-off cavaliers, or even parliamentary forces, would’ve chanced producing a product like the OP coin? It could also be a very easy target for forgers in the new commonwealth period couldn’t it??? ?
edit: some confusion...i was talking about the cast-like bubbles of the reverse, you were obviously referring to the irregularity of the bottom ‘die’