The Navy's Limited Duty Officer program is constantly being re-examined and re-evaluated, especially in light of its necessity among the various “enterprises.” Because of the proliferation of other means for enlisted personnel to become commissioned officers, as well as the Chief Warrant Officer Program and the expansion of training for Petty Officers, the number LDO “designators”—four digit codes that identify officers for use in personnel management and for identifying an officer’s status, and which are analogous to the ratings for enlisted Sailors—has dropped from 30 in 2011 to just 10 in 2016.
The current designators which LDOs are eligible for consist of four submarine-related fields (Engineering/Repair, Ordnance, Electronics, and Communications), Aircraft-Maintenance, Administration, Information Systems, Security, and the Civil Engineer Corps.
Understanding the LDO/CWO Designator system is quite easy. The first of the four digits indicates whether the officer is an LDO (6) or CWO (7). It’s followed by a number between one and five that designates the general category in the LDO/CWO community; 1 is for Surface, 2 is for Submarine, 3 is for Aviation; 4 is for General; and 5 is for Staff. The third number represents an LDO or CWO technical specialty, and the final number represents the officer status—a 2, for example, means “a temporary officer of the Regular Navy whose permanent status is enlisted.”
You can get a better idea of how this works by looking at NAVADMIN 045/16, the results of the LDO/CWO Selection boards that were announced on February 25, 2016. The first LDO, who was selected for Ensign (the grade all LDOs start at), is listed under Engineering/Repair Submarine with an LDO Designator of 6235. The 6 means LDO; the 2 means Submarine; the 3 is for the technical specialty of Engineering/Repair-Submarine; and the five indicates that the newly appointed Ensign is in the Navy Reserve (with some caveats).
Limited Duty Officers are rarely seen in Staff Corps such as the Judge Advocate General’s Corps. In fact, the LDO positions for the JAG Corps has been eliminated, with enlisted Sailors in the Legalman rating assuming many of the duties that LDOs in the JAG Corps performed. Currently (2016), the only Staff Corps that has an LDO program is Civil Engineering, with an LDO Designator of 653x.