I have a single barrel, single shot shotgun that belonged to my great grandfather. It is stamped US Patent Sept 6, 1964. Impressed in a steel plate behind the trigger guard is 5559 (production nymber?). I know it was made between 1864 and 1886 because of the name. Can the date of manufacture be determined from the 5559 stamp. The gun is in superb condition and I am sure it has not been fired for over 100 years. Thanks