Kim,
...All of us on this forum are glad to help. We actually enjoy getting PICs of old Randall knives and discussing when they were made. Many of the older knives are very valuable. You are right that there are many different models of these knives. There are actually even two different Models that are 6 inch Model 12s. One of them is the 12-6 Little Bear Bowie and the other is the 12-6 Sportsmans Bowie. There are many cues including the shape of the blade and hilt and even the thickness of the spacers in the handle that can help to date a Randall knife. The sheath and how it is sewn and also the button snaps and even the color and markings on the sharpening stone are also cues for dating these knives. I am usually pretty happy if I can date an old Randall knife within 5 years. Some of the people posting on this forum can date them within a window of just one or two years.