guns-
Most regular army units did not stamp their weapons during the Kragera. Stampings could be from national Guard, state police, VFW, whatever... The SN on your rifle indicates it was made after the end of the Spanish American War, but it could have see service in China or the Philippines, or maybe Mexico.
there are guys on the Culverlist who can give you more info - perhaps.
Welcome to the club!
jn