The discoloring and missing blueing shown in your last photo looks exactly like the finish damage on a model 15 suicide that I own. No pitting , just missing/discolored finish. Also the discoloration of the trigger is a match. I would post pics but am on the other side of the Planet at the moment. The suicide history creeped me out at first , but after shooting it became just another firearm to me.
First thing I noticed about this gun when I bought it was the odd discoloring. None of the other guns I own or have come across look like this.