Hello to everyone. I am trying to figure out the age of my new purchase. The serial numbers start with a 5 and end with an M. This seems to date my gun to about 1977. However, this gun does not have an ejector rod shroud on it. The ejector rod is exposed as the second issues were prior to 1973. It there anyone here that can help me to understand what is up with this gun. I bought it from the original owner. It is in excellent condition. I love the size of this gun and am just curious as to it's age. I have attached this picture to help. Any insight would be greatly appreciated.