Note1: the design origin (including side-block fret marker seen on JTK1) might can be dated back to 1959 Marco Polo "TL-59", produced by Guyatone, manufactured by Kiso Suzuki Violin:
1959 Guyatone Marco Polo "TL-59". PulseBeatGuitars.com. "The story of this rare Marco Polo guitar started as a production design under the direction of Guyatone House-Brands in 1958. It was built at the Suzuki [i.e. Kiso Suzuki Violin] ... The Marco Polo was styled, more-or-less, after the Fender Jazzmaster-shape with its offset guitars waist. ... extended upper horn and backward sloped lower cut-way. ... Guyatone was also particularly known for their "Gold Screen" pickups. Featuring a Rosewood Fingerboard with Side-Block Fret Markers ..."
Note2: relating model, St. George MJ-2 by Teisco seems to be exported as late as circa 1963.