LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) is a special application of Code 39 used by the U.S. Department of Defense and is governed by Military Standard MIL-STD-1189B. The Standard defines acceptable ranges for a number of variables, include density, ratio, bar height, and size of the human-readable interpretation line.
The Modulus 43 check digit, optional with Code 39, is defined and recommended in the specification. While not required by the general specification, it may be required in specific Department of Defense applications. Be sure to check the requirements for your project or contract.