B67-74 LOCKING T-BEVEL. Smith & Duckworth. Patented in 1883 by James Duckworth and Eli Smith of Springfield, MA. The blade has a groove milled in it which allows it to be quickly locked at a 90 degree angle with a sliding thumb-operated lock. This one has two small screws on the end, which require a screwdriver to tighten. 4" steel handle with 7-1/2" square cut blade marked with the patent date. A very uncommon bevel. From the collection of Steve Dice. Fine 200-400