WABCO 15" Circular Slide Rule

Here is another fine product from Perrygraf Corp (still going strong!) The copyright date is 1964. This slide rule is 6.5 inches in diameter and sports a nifty plastic arm -- advanced sliding technology! Actually, it's not all that advanced. Time and, presumably, heat have slightly shrunken the plastic arm and it's actually difficult to turn. No matter. This seems like a pretty useful wheel to me. Too bad about the shrinking arm, though.

Otherwise, this wheel is in good shape. It's made of a sturdy, plastic-coated (sort of) cardboard.