Send pics to Billy Schick...
He may have built that cue
Joss did 5/16x18 in 68/9 and 73/4, and Scruggs did in 78.
Joss did use a 5/16x18 thread. Kenny Dodd's Joss made in 1969 has a 5/16x18 thread as I recall. I don't remember Joss making rounded off corners on the butt inlays. Could it be a Bert Schrager cue?