Buffalo, NY: American Optical Company c1967. First Edition. 9 pages. 8 1/2 x 11 inches. Stapled, publisher's wrappers. Contains principles and parts lists (with blow-up parts diagrams) of the Model 41T and Model 42 with #615 illuminator microscopes. Creased. Good working copy. Good. Wraps. 
A useful reference for those still using or looking to repair these instruments. A classic instrument used in thousands of biology and science labs throughout the 1960s.