Slide showing Fig. 90 - three diagrams of unidentified subject. Slide shows Fig. 90 - three diagrams of unidentified subject. There are 9 sets of letters in this diagram, which are: 'S', 'R', 'C', 'D', 'S+d', 'S+pR', 'S+pC', 'S+pD' and 'C+pD'. Late 19th to early 20th century