From the California Military Museum archives:
An unidentified infantry sergeant of Sacramento’s Company E (former Yuba Light Infantry) 2nd California Infantry Regiment (now the 1st Battalion, 184th Infantry Regiment [Second California]), National Guard of California. Circa 1906-1912. It is a really nice cabinet photo of a pre-WWI infantry NCO.
This soldier is attired in the Army’s standard M1902 pattern new service dress uniform complete with a six-button dark blue coat and cap with service cords. He has an early model Springfield M1903 .30-06 rifle at the ready, which only began replacing the Guard’s Krags in about 1906. The rifle’s companion 20-inch spear-point M1905 bayonet is on the sergeant’s belt, another new item that only began fielding in 1906.