This is a picture of the 1942 supplement NEC book. These supplement books were printed to save paper because of WWII. Instead of reprinting the whole book they just printed the changes.Somewhat rare but can be found. It has 38 pages with a "S" after each number. Ex. "38S". Some of these supplements are found in the front of a 1940 booklet and will say "with 1942 supplement" at the top and bottom of the cover page. Some say this at the top of the 1940 NEC book but doe not have the supplement in it that I have found. It must say it at the top and bottom. This is printed on VERY thin white paper.