|What's the difference between a LtCol and a LtCol Brevet? |
The pay check.
Let's use the rank of Major as an example of how this would work:
You halve the number of authorized regular Majors in the Marine Corps. When the board for Major convenes, you select for regular promotion the number of authorized regular Majors. You then have a secondary selection for brevet Majors to fill 04 billet line numbers. They are maintained at the 03 pay grade, but they wear the rank of Major, receive the experiences of an 04, and in the following board, after they've received one observed fitrep (or a certain amount of observed time, much like Career Designation), the Brevets are in zone for regular promotion. Any that don't meet the muster for regular promotion (i.e. pay increase), fill out their Major tour as Majors, when they finish they revert to Captain, and are subject to the career limitations of a Captain. For those who are brevetted that don't make the cut, an equal number of regular Captains will be subsequently considered for regular promotion to Major.
You can do something similar with each rank from Captain to and including Brigadier General. However, you have to be a regular Captain to have Company/Battery command, a regular LtCol to have a fleet Battalion Command, a regular Colonel to have a fleet Regimental Command, and a regular Brigadier to have MEB command.
One caveat to this is if you are a Major, or LtCol that has been brevetted to LtCol or Col, if you spend more than one tour as a Brevet LtCol or Col respectively, upon retirement you maintain the title, though you are not owed nor given the appropriate pay.