1951. Fourth Edition. 368 pages. No dust jacket. Blue cloth boards with gilt lettering to spine. Black and white diagram throughout. Pages and binding are presentable with no major defects. Minor issues present such as inscriptions, mild crinkling and light tanning. Page 336 is significantly dirt marked. Boards have mild edge wear with light rubbing and crushing. Some light marking and tanning. Boards are bowed. Book has a slight forward lean.