There is no central repository for all DoD contracts. The OSD/JS FOIA Requester Service Center services contract requests, with a few exceptions, for the Defense Advanced Research Projects Agency, Missile Defense Agency, Defense Micro Electronics Activity, and Washington Headquarters Services. You MUST include the contract number in order for this Service Center to process your request.
Contracts administered by the Military Services, the Combatant Commands, and other Defense Components are not under the control of this Service Center and must, therefore, be directed to the appropriate office for processing.
Please note that contracts are only maintained for six years and three months after the termination of the contract. If you are still unsure of the contract number or which DoD component has purview over the contract, you may wish to begin your search at the Federal Procurement Data System website.