This is a bit of the Keilwerth history that I've found scattered across a couple of websites. It's incomplete. I'll be publishing the full version on my website in a bit. Please add to it or dispute it if you have further information.
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By 1920, Johann Keilwerth, Julius' father, was active already in the building of woodwind instruments in Graslitz, Czechoslovakia.
Johann had three sons Max, Richard and Julius (1894 - 1962).
After his apprenticeship, Julius Keilwerth first worked for the Kohlert company in Graslitz.
Julius and Max established their own workshop -- in their home -- around 1925. They primarily manufactured saxophones for the Adler company.
After end of World War II in 1945, the Keilwerth company was "expropriated" (or "nationalized") and the workshops in Graslitz were taken over by the Czech collective combine, Amati. After this "expropriation", Julius Keilwerth fled to Nauheim, Germany and dared a new start with a large facility in 1947. This company was handed over in 1962 to Julius' son, Josef Keilwerth, and was then sold in 1989 to the French company Buffet (from the group of firms owned by Boosey & Hawkes).
From approximately 1970 on, Keilwerth concentrated exclusively on the building of saxophones.
Before the Second World War drove Julius out of Grasliz, Keilwerth produced saxophones under the four model designations Toneking Special, Toneking, The New King and King. After the move to Nauheim the models produced were the Toneking Special, Student [The New King], and Toneking Exclusive.
The New King, already well-known from Graslitz, was built until 1970.
In 1987, the Peter Ponzol model was introduced. The Toneking gave way to the SX90 and the New King gave way to the EX90 (and at the beginning of the 1990's, the ST90).
Around 1992, the ST90 Series II appeared (the ST90 III and IV are now offered) and the high-quality Peter Ponzol model gave way to the SX90R.
The brother of Julius Keilwerth, Richard Keilwerth, worked from 1945 to 1951 with Amati to integrate the Grasliz-based portion of his father's company.. He has since moved to Germany and manufactures flutes and clarinets in addition to saxophones. The saxophones are offered under the designation 102 to 105.
Max Keilwerth (1898 - 1968) likewise began his career in Graslitz, where he manufactured saxophones in his home for the Adler company, in Markneukirchen, Germany.
Starting in 1923, Max Keilwerth developed the saxophone department for the Graslitz-based company F.X. Hueller. In 1925, this company became independent, but Max still supplied saxophones to his former employers, Adler and Hueller, from 1925 until the early 1930's.
After the Amati expropriation of Keilwerth in 1945, Max Keilwerth worked for Amati for a short time, but left for Trossingen, Germany in 1949 and began building saxophones for the Hohner company.
These horns were manufactured until about 1967 under the model designation "Hohner President".
(From
http://www.klaus-a-schneider.de/facharbeit/seiten/deutschland.htm. Translated by
www.altavista.com. Transliterated by saxpics.)