BUREAU of AERONAUTICS, covering all types of MFGing of Aircraft like B17, B29 & other war birds. These were issued to my Dad, Tooling Engineer with Boeing 1940-1982. "MANUFACTURING OPERATIONS" OF THE TIME =1943 All are in very good shape. Very collectable & were Securet back then, can be found in up-todate AC 43.13 My interest was in Spot Welding that was used back then, I build one spot welder. Sold in a set of 26 only. PLEASE TEXT MY CELL. Shipping & handling is extra.