Each record in ST is identified by a serial number.
When referring to a specific ST item (a.k.a. record), it is customary to use the syntax "ST #NNNNN". This syntax is recognized in comments etc. and in the WWW interface is converted to a link to information about the record (usually the record update page).
When specifying this field in a customized sort or display, any of the names "Serial #", or "#", can be used.