I was thinking two sizes of shell casings. That would make the lines in a circle incuse on the coin. Probably the larger one was applied first, then the smaller one centered.
The reverse highest points show a slight amount of contact that flattens them a bit. But if they used a spent round, the round would absorb most of the hit to the coin and bend. That is what I'm seeing on your coin.
The metal movement to make the reduced areas lower, made the area next to that rise. The highest point is the normal profile of the bust. But the metal movement raised the internal areas higher.
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