Complex sentence: Even though the Navy Officer Sword is older, 1852, it was discontinued until reauthorized during the (1900s) the M1859 Marine NCO sword is the oldest weapon in continued (unbroken) service still in U.S. inventory.
Split into simpler sentences: Even though the Navy Officer Sword is older (1852), it was discontinued until reauthorized during the 1900s. The M1859 Marine NCO sword is the oldest weapon in continued (unbroken) service still in U.S. inventory.