My first post on the forum! I inherited my fathers mid 1950s M&P late last year SN C 322xxx. He carried this revolver as a Fort Worth police officer up until about 1970 when he was promoted to detective. It is in fine shape with only normal holster wear. It is my understanding that if it is not a model 10, no +P ammo. What magic wand was waved over the guns when they were given the model 10 designation. If memory serves me, I believe that this is the first gun I ever fired when I was around eight or nine...Dad helped me hold it. When I was a kid anytime Dad went to the range to qualify, He always had either my brother or I clean it and oil it. He would then inspect the job we did, load it and return it to it's holster. True firearms education.