Published by U.S. Divers Corp., California, 1956. (Top) [ps]
Also 1959 (Below)
From eBay:
The book measures 5 1/2" X 8 1/2" and has 85 pages. (This must be 1959 edition. 
A comprehensive instructional manual illustrated with over 90 drawings and photographs. Includes maintenance and service instructions for the "Aqua-Lung" regulator "DA", "DW" and "DY", there is also an underwater sign language alphabet illustrated.
An scarce and interesting instructional manual, it will be a nice item for any diving enthusiast.