The staff Working Timetables (WTTs) give details of the headcodes to be displayed, each volume having a summary in the introduction, with the actual headcode for each individual train given in the tables themselves.
On the Scottish Region the WTTs were issued in five sections, A through E. By 1978, a G prefix was added, making the sections GA through GE.
Below are an example from each section, with the cover, the map of the area covered, and the pages with the headcode summaries being shown.