This may be basic, but I'm at a loss. Can someone explain or point me to a reference on how to tell if my model 97 is a riot or trench gun? It's labeled as a Winchester Model 1897 and has the short barrel. I inherited it from my Dad who used it in Viet Nam. There's a E above the s/n and what appears to be Winchester stamps on the barrel and action. I can post pictures if that would help. Thanks in advance.