This has come up before with coins of very similar shape. That thread came to no conclusion regarding origin that was acceptable to all commentators.
In my view a coin reduced drastically by clipping can have only a small premium value over silver - otherwise forgers will get out their tools and convert cull coins into higher valued clipped coins. These do seem to be relatively old but since no one recalls when or why the reduction took place they are curious - possibly rare - but of limited actual value.