How much did you pay for those Morgans? They do have melt value even if they don't have much numismatic value. I was wondering about toning on my Peace Dollars I got in a lot along with a lot of Indian head Pennies
Looks like they where wrapped or rolled and where in a fire. The oxidation is pretty irregular; I don't think being stored in a damp place would give them such irregular spotting. My guess.
As extreme as they are, any treatment to remove the deep black areas chemically will make the untarnished area extremely obvious as they become raw appearing. Jim