When G&L released a number of models with a Kahler™ 2320 flat mount fine-tuner vibrato in 1985, a U-shaped bracket was not good enough to provide sufficient tuning stability. Another one of Leo’s inventions came to the rescue: a string lock mechanism behind the nut (see this 1985 Rampage). It is covered by US Pat. 4,517,874 (filed June 19, 1984) and ensures a proper string angle over the nut while still providing easy access to the truss rod nut, as seen below on a 1986 Superhawk w/Kahler below. This clamping mechanism was licensed to GuitarTech and this is the brand name one sees stamped on the plates, together with “Pat. Pend.”. For comparison, check this 3rd style Interceptor HSS for a high-end aftermarket string clamping solution.