I just bought a Weatherby rifle from a classified ad in my home town. It is a Mark V of some sort, very light rifle. I thought it might be an ultralight, but it has black plastic stock, not a Medalist. Anybody know how I can tell what model it is? Can i tell by the serial number? It starts with a WB. The gun has a thin barrel, not fluted and it is blued metal. Any ideas on how to find out?