(click on pictures to enlarge)
According to advertisements of the day, this was "The Pencil with a Brain" and by any standards is near the top of the scale as far as ingenuity. The earliest reference I could find to the Roller Rule was an ad in the November 27, 1948 issue of The Billboard. There was also a write up in the May, 1949 issue of Popular Science, which identified the maker as Roller Rule Sales Co. of Los Angeles. An advertisement in Popular Mechanics from February 1956, says: "Precision made, accurate, handy. Roll it over any surface. Measures curves and straight lines, any shape, any distance, Excellent pencil too. A must for architects, engineers, carpenters, plumbers, painters, students, pilots, navigators, etc. Available in inch or nautical measurements. Specify choice. "In attractive gift box" Roller Rule Mfg. Co., 1319 Gavieta Ave., Long Beach 13, Calif.
Most examples have a washer style clip; this is the only example I have seen with a pressed clip.
An example recently surfaced marked only "Japan" on the clip. The papers included with that item read "Made for Chadwick-Miller in Japan."