The Unique Soldier Boxes can be purchase once in the shop for 1200 
, or it can be obtained in the Arena
Currently the prizes available from the Unique Soldier Box are:
Point Man
870 Blue Skull
Bahamut Origin
Guardian Coral
SA-12 Leo
Veresk Dragoon
VP5K Project CO.9
Rifle Man
DT-42 Coral
MA-47 Gold Dragon
MA-74M Argus
Temporal Platina
WCX-SBR Red Eye
X4A1 Graffiti
Xako RK.95 Chrome
X4 SOPMOD Block II
Sniper
Epko Firebird
G93 Old Machine
SR-F2 Legend
Zaystev Custom
Zebra Cyclops