Rank 1000, 500, 9/2 and 50? (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

C(Roman numeral for 100) + O(letter representing 0) + L(Roman numeral for 50) + O(letter representing 0) + NE ( 2 out of 4 letters of “nine”/9 divided by 2) plus ( and ) L(Roman numeral for 50). Defn: … in the military.