Symbol names end in .sym. The only symbol filename convention that is used in gEDA/gaf is that if there are multiple instances of a symbol with the same name (like a 7400), then a -1, -2, -3, ... -N suffix is added to the end of the filename. Example: 7400-1.sym, 7400-2.sym, 7400-3.sym...
Schematic names end in .sch. There used to be a schematic filename convention (adding a -1 .. -N to the end of the basename), but this convention is now obsolete. Schematic filenames can be anything that makes sense to the creator.