The SYMBOLSET is used by TEXT elements to determine which set of characters to use.
The alphanumeric "identifier" for the default symbolset is "19U". Note that while some characters (e.g. A to Z) commonly map to the same character in different symbol sets, other characters are likely to map to different characters. Thus you may only notice that the wrong symbolset is in use when accented characters or mathematical symbols are output inappropriately. For example, plusminus in 19U (equivalent to Microsoft® Codepage 1252) maps to Yacute in 8U (HP's Roman-8), and a checkerboard in 10U!