When you say, this machine wasn't salvageable?? any good body guy can cut out and reweld new metal in that area... I have it done all the time as 90% of all machines I restore have some degree of rust in this area... and I replace the bottom pans in all of the machines I do.. so don't let it scare you off too much ,anything can be fixed with proper knowledge.
Here it is pretty bad. When you take off the liner, the first picture shows you how bad the damage is caused by the condensation/moisture that's not properly draining. If you look at the 2nd picture, right above where the compressor would be, you'll see the damage that ate from the inside out. This is called beltline rust as it usually goes around the entire machine. If you have damage on the back, more likely than not you'll have damage on the sides that need repairing. Needless to say, this machine wasn't salvageable.