Glock, You can put it down in good old KO oil out of your heater and let it soak over night. Then the side plate should pop off. While you are at it after the soak, put some Remington oil on the rust area and under a bright light go over it with steel wool. 4 or 5 - 0 will do the best, and go easy on it, very little preasure. The rust should come off easy. Take your time and treat it with kit gloves .