Coin shop had a small bin of coins which appear to have been damaged in a fire. I picked up this one because the combination of oxidation and carbon deposits gave it an odd sparkly texture on the obverse. Otherwise, it's quite ugly and not worth more than it's 0.500 silver content. But I thought it was at least interesting. (I should list it on eBay and claim is has "monster toning"!) 1/2 Crown, 1946, UK, George VI, incinerated
I'm not necessarily disagreeing with fire damage- I think that's as likely a scenario as any- but there could possibly have been other environmental factors involved there.
The dealer told me they had been in a fire. I assume he heard it from the former owner. It was a mix of coins, a few silver but nothing that struck me as particularly valuable. The half crown is quite sparkly in a way that doesn't show up in photos. I assume that is has carbon deposits and the damage is not all oxidation.