A lot of the codes (like the #) vary from one area to the next so you really do need to get some kind of key in order to be sure of what they mean in your area.
"OD" almost always means "Open Discussion Meeting" (anyone can attend and the meeting format is open discussion on a topic that will either be introduced by the chair or from the floor, depending on the particular group), so that would probably be a good place to start and you could ask someone before or after the meeting what the other codes signify in your particular area. Actually any meeting the code for which starts with an "O" will be an open meeting; any meeting the code for which starts with a "C" will be a closed meeting -- which means only self-identified Al Anon members should attend. "S" usually connotes a "Speaker Meeting," which means that a significant portion (and in some cases the entire hour) will consists of a pre-identified speaker telling his/her Al Anon story.
freya