I would venture to guess that the
abbreviations originate from the need to condense information on a little piece of paper that goes in a
flip (or on a small envelope). There is no master plan for
abbreviations. Generally if you collect in a particular
field, you know or can figure out the
abbreviations. I would not expect a convenient list, unless of course, you want to make one. I have a friend who spells out all of a reference works' names, but he is a master at making little tags. Most
abbreviations are simple truncations.
SNG ANS for
Sylloge Nummorum Graecorum American Numismatic Society, SG for
Sear,
Greek coins and their Values, or sometimes just 'S' and the appropriate number. You already know the coin is Greek, so this 'S' means
Sear,
Greek Coins and their Values. You can see how people, short of space, do
abbreviations instead of the full names. Especially since more than one reference may be cited on a
flip. Sometimes a particular abbreviation is more a function of the font size that you chose ahead of time, not giving yourself enough room for a more extended version of the name.
I am serious about doing your own list if you have the time and inclination. If you are inclined, please share it too.