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.