Very interesting Paul....as a young draftsman around 1961 I worked for an engineering company in Mississippi...one of the many things we did was create these quad sheets for the COE......it took about 6 or 7 drawings on mylar to make one quad sheet...one drawing would be the woods (green areas)....another the waterways (blue)....another one roads.....another one the houses, contour lines and powerlines, and another all the writing.....etc.....it was very tedious but interesting.....