It is common if dealing in defense or military subject matter, to list in the salutation of a letter or memo your military affiliations such as:
Very respectfully,
Joe Bloe
COL(R) USMC
On the other hand, in everyday regular, communication (not related to the military) - verbal or otherwise - others may refer to you by your previous, active service rank as a sign of respect; however, IMO it's a bit self-serving to refer to yourself in that way.
Last edited by Offshoreman; 09/29/23.
