Contact Chris Batha. He has the Boswell records that should cover your gun.
I had 12990. It was a side lock and pre-1898. It has moved on, via Kirby Hoyt, years ago.
I have a composed pair of Boswell guns. 13459 was Sept 1, 1899. The matching gun was built Sept 1902.
Contact: abby@cornellpubs.com, for a 1910 catalog copy. Abby may have earlier Boswell catalogs.

All best,
Joe in Charlotte.

Photos?