Heads-up for you staff officers, admin officers, and yeomen out there, the new Department of the Navy Correspondence Manual is out on the street.
You can download it from this website - 5216.5 about mid-way down the page.
Tangent: Rank Abbreviations
Ask any of the junior officers who have worked for me in my past few jobs, and you will find that one of my administrative pet peeves is incorrect rank abbreviations. Navy rank abbreviations are written in ALL CAPS with no punctuation.
Incorrect: LTjg or LT(jg) or LT(JG)
As a point of reference, you will find the DON Correspondence Manual, Appendix A "Military Models of Address" shows how to address letters to people of various ranks of all services, and shows the proper abbreviations for each rank.