Doylenator,
If the hinge pin is REMOVEABLE, your gun is a MODEL 1900. This series was marketed from 1901 to circa 1916. The Model 1908 has a snap off forestock and a NON-REMOVEABLE hinge pin. Check out the pics.
In either case, with that low serial number, your gun is at least 100 years old - it was originally chambered for the 2 1/2" period shells, later versions were chambered for 2 3/4" shells. If I were to shoot mine, I would stick to the lightest payload, lowest velocity, smallest dram equivalent 2 3/4" shells available.
Production of the 1908 began circa 1909 and ran in two series up to 1942, when it was modified to become the Model 48. BE CAREFUL and BE SAFE shooting these old shotguns. ALL H&R shotguns made prior to 1948 had non-self adjusting barrel latches and after extensive use may have a very light lock-up - meaning barrel could unlatch and open up during firing of heavy loads - I've actually seen this happen one time with an old Crescent made single barrel. Not a fun experience.