How do i determin the grade of my Ithica double 16ga. ser# s383177? It has an F on the watertable over the 16. A 4 and a two stamped on the barrel flats Top of barrels say Smokeless Powder Steel made in USA. Rear barrel lug has what looks like Nitro Pow and thats all i can see of that and also on barrel flat is stamped a large D as the base of the extractor. And i have never seen the letter S in front of an Ithaca ser#.

Thanks

Tommy