The two sided letter is addressed to Einsteins fellow mathematician Herman Müntz and deals with Einsteins unified theory of Distant Parallelism that he sent to the Prussian Academy on August 19th 1929. The paper was not published until 1930 and the letter informs his friend about the central parts.
Herman Müntz (1884-1956) was a German mathematician, now remembered for the Müntz approximation theorem. Born in the Polish part of the then Russian empire he moved to Berlin and later Münich. In 1927 he worked closely with Einstein. In 1929 he took a professorial position at the Leningrad State University. But as a German citizen he was expelled from the USSR in 1937 moving to Sweden where he lived for the rest of his life.
The letter is a personal gift from H Müntz to the present owner´s father for services rendered regarding help with construction drawings and patent Procedure from mid 1940´s onwards.
Einstein´s paper regarding his his unified theory of Distant Parallelism was published in 1930 but after 1-2 years Einstein becane aware that the construction did not work.
A young researcher, Herbert Salzer, proved in a letter 1938 to Einstein that his 1930 article (and thus the letter included in the sale) had inaccurate equations. Apparently Einstein had confused the different property assosiated to the Latin and Greek letters. In his letter answering Saltzer he writes: “Therefore your transformation equation is correct, mine wrong”.