why??

[ausjack]

anyone have any ideas why we get coins like the one in the middle?? it's not just one side so here's a quick scan

[Goldseeker]

Most probably because the coin has been in some form of water/contaniment.

[runway]

The middle one looks like an old 50c from 1970s

[Fulvio]

anyone have any ideas why we get coins like the one in the middle??

Its oxidation. Probably a reaction with atmospheric gasses rather than fluids. I've seen freshly-minted examples, and I've wondered if the planchets could have been affected. Not done any research though, so its all just guesswork.