Defense Priorities and Allocations Systems (DPAS) consist of four ratings:
Definitions of each rating is located in section 700.11 of the link below.
This information is taken directly from the “guidebook” link below.
“The purpose of DPAS is to assure the timely availability of industrial resources to meet current national defense and emergency preparedness program requirements and to provide an operating system to support rapid industrial response in a national emergency. The Defense Production Act of 1950 authorized the President to require preferential treatment of national defense programs. Executive Order 12919 put Department of Commerce in charge of program. 15 CFR 700 provides rules for DPAS program. DoD 4400.1-M provides guidance for DoD activities.”
“All prime contracts, subcontracts or purchase orders in support of an authorized program are given a priority rating. A DX rating is assigned to those programs of the highest national priority. The President has to approve a DX rating for a program. A DO rating is assigned to those programs that are vital to national defense. The Secretary of Defense has to approve a DO rating for a program. An unrated order is a commercial order or a DoD order that is not ratable. A DX rating takes priority over a DO rating which takes priority over an unrated order. Rated programs are also given a program identifier symbol. Examples are A1 for Aircraft and A3 for ships. The program identifier symbol does not, by itself, indicate any priority.”
This website is the main DPAS page, and has additional information.