My father gave my a Savage 220D 16 Ga on my 8th bday back in 1989 and have recentkybtaken it out to take it down and clean it. Upon removal of the forearm, I noticed a “B” over “LI” on the underside of the barrel. As for the date of mfg, would I go by the letter B (1951 mfg)? Thanks in advance.