The use of a piloted micarta joint, the style of the cue itself, the point work, makes me think that this possibly would be the very early work 70s into 80s of a cue maker who possibly became more well known as they progressed. The long 5/16 18 pin may have been an early experiment by the maker that was later shelved on future cues.
I know that you have touched hundreds of cues- so if the cue butt weight, overall cue balance, the sound of the shaft tapped against a cue ball, all denote the feeling of some quality in the build, then I would bet on early work of a cue guy who became more successful and started signing cues at some point.