The front of this rule is a pretty basic trig rule, essentially a single-sided version of the N1010-ES, minus the CF and ST scales. The back, though, has scales like "Ground Size", "Ground Speed", "Image Size", "Altitude", and "Focal Length", along with instructions for obtaining image speed and ground size for an aerial photograph. Just the tool if you're out in your U-2 looking for documentary evidence of covert missile installations. The back also says "US Air Force Aerial Photo Slide Rule type A-1". The rule seems to be made of magnesium with aluminum plating, or at least the degree of oxidation on the rule when i got it would seem to indicate that (ok, it could be just aluminum. i really have no idea how i'd go about figuring it out). I managed to clean it up with some 220-grit sandpaper, though. You can kill me later for taking sandpaper to an "antique". Though the rule says "Stafco" on it, i'm virtually positive it's a pickett rule. Why? hey, who's the collector around here, pal? This came in a kit with some really nice rulers, pencils, and a big drafting rule thing, all for a measly ten bucks. I love flea markets.