We got the germ of the idea for the cam locking mechanism on these sliding bevels from a model made in the early 1900s.
We improved it substantially, making a better mechanism of bronze (using the lost-wax process), combining it with a stainless-steel blade and housing both in a resin-impregnated wood body; it could be used under water without damage.
The obvious benefit of this design is that the locking mechanism is completely flush, allowing the bevel to be used on either side. But more important, it can be used in the most restricted places, since the lever cam lock can be operated with a single finger. You can reach way back into a corner to measure angles. Since the locking mechanism operates by compression with no rotary movement, accuracy is perfect. This is the best sliding bevel design on the market.