yes, but that is an entirely different type of saxophone.
If it bears JK ( Julius Keilwerth) best in the world logo, and then Czechoslovakia , this is not Max Keilwerth saxophone ( which would have a " Pure Tone " trademark)
The only saxophones that may have both, are either the Keilwerth made in Graslitz or the successive Amati-Lignatone made in the same factory once it was nationalized. Max Keilwerth made saxophones for other companies as well as for himself.
Julius Keilwerth (12.04.1894 - 14.11.1962) first apprenticed for the Kohlert company in Graslitz, Czechoslovakia. After this apprenticeship, Julius Keilwerth and his brother, Max, established a workshop in their home around 1920. They primarily manufactured saxophones for Adler and F.X. Hüller. The Julius Keilwerth company was founded in Graslitz in 1925, when Julius started making alto and tenor saxophones. Once these two saxophone types were extremely successful, he began making sopranos, baritones and, upon special order, bass saxes. Soon 100 employees worked in the Keilwerth factory, and an additional 50 were homeworkers. The Julius Keilwerth company became one of the largest saxophone manufacturers in Europe by the start of WWII, with approximately 150 workers. In 1930 he built a factory with a house at the Silberbacherstrasse 1348 (now Havlíčkova). In 1937 despite the crisis he extended the factory. In 1938 Julius Keilwerth bought the villa of Anton Richard Breinl, Lipova Ceste 17.
Keilwerth factory, Silberbacherstrasse 1348, Graslitz 1930 Former Keilwerth factory, Havlíčkova 1348, Kraslice Breinl villa where Julius Keilwerth lived till 1946
After WWII the family was forced to leave Graslitz, like most of the German speaking population in Bohemia. Most people were only allowed to take 50 kg (110 lbs) of luggage on the train with them. Julius Keilwerth, then aged 52, is mentioned on an expulsion list for train 15, wagon 33, on Sept 12th 1946 destination Bavaria. He went with his wife Franziska (28-10-1895-21-07-1971), son Josef (27), his wife Hilde (22) and the little Gerhardt (1).
Julius Keilwerth first went to Nordhessen and in 1947 settled down in Nauheim, near Frankfurt. Other instrument makers also had settled down in Nauheim, due to an active policy
of the local authorities. On January 29, 1947, the Julius Keilwerth Company started its operations in the laundry room of the Bäckerei (bakery) Stelzer at Bahnhofstrasse 9, Nauheim. There they employed 5 people, and did saxophone repairs only.
The old Julius Keilwerth production facilities in Graslitz, now Kraslice, in 1948 became part of the Czech Amati collective. Amati was a forged merger of all regional competitors. The first saxophones that Amati sold were still stamped with the "JGK - Best in the World" trademark, had the model name 'Toneking' and had Julius Keilwerth serial numbers.
In 1949, the Keilwerth company moved into a new building at Königstädter Strasse 101 in Nauheim. Later the company also opened and maintained a subsidiary division on Helwigstrasse in Groß-Gerau, 5km from Nauheim. In 1953 Keilwerth had some 50 people at work (home workers included), making not only saxophones but also trumpets and trombones, and repairing all kinds of wind instruments. Most of them were old employees from Graslitz. In 1956 a cheese-making in Groß-Gerau was bought to give room for the metal wind instrument making. In 1962/1963 the Offenbacher Architektengemeinschaft Novotny & Mähner designed and built a new factory at the Königstädter Strasse 103, four pavillons with an inner court. Here the operations from Nauheim and Groß-Gerau were brought together in 1964.