I just bought one off CL. It's a 2017 American Professional Exclusive from Chicago Music Exchange. Somehow the previous owner had broken the threaded trem arm off in the socket (collett?). He had bought a StayTrem arm/collet but hadn't installed it. Easy install. Arm now snaps in with a satisfying thud. No threads. I really like it. Now I understand why JMs get the accolades for the tremolo. They stay in tune wonderfully, and the mechanism itself (at least the StayTrem version) is noiseless and solid feeling. Thought I'd pass this along, in case it helps anyone. I think the previous owner was just irked with the guitar because of his trouble with the original trem. I got a good deal.