David --
Andrew is right, and your Augusta source is right as well.
The "Washington Guards", Capt. Laurence J. Guilmartin served at Fort Pulaski and Fort McAllister. Earlier it was assigned to Olmstead's 1st Georgia Regiment. Later the company joined the 22nd Georgia Heavy Artillery Battalion as Company "E".
As we discuss companies like the "Washington Guards" we need to understand two facts --
1) More than one company could share the same name. The copyright laws have no bearing here.
2) Over time popular companies like the "Washington Guards" attracted more recruits than could be carried on roll. For that reason (and others like it) companies divied, sometimes more than once, so that two or more companies having a common origin entered Confederate service under the same name.