Career
In 1920, he tied for 2-4th in Canterbury, took 10th in Berlin, and tied for 4-5th in Kulmbach. In 1921, he tied for 8-9th in Hamburg. In 1922, he tied for 2nd-3rd in London (Major Open).
In 1922/23 he tied for 6-9th in Portsmouth/Southsea.
In 1923, he tied for 6-7th in Triest. In 1924, he took 13th in Győr.
In 1925, he tied for 6-10th in Debrecen. In 1926, he tied for 6-7th in Milan, and tied for 3-4th in Scarborough.
In 1927, he took 2nd, behind Stefano Rosselli del Turco, in Naples, and tied for 3-4th in London.
In 1928, he tied for 3-4th in Cheltenham, tied for 4-5th in Dortmund, and tied for 1st-2nd with George Koltanowski in Tenby. In 1934, he tied for 3-6th in. In 1935, he took 2nd, behind Samuel Reshevsky, in Great Yarmouth.
In September 1939, when World World War II was broke out, Seitz along with all German players (Eliskases, Michel, Engels, Becker, Reinhardt) and many other participants of the 8th Olympiad in Buenos Aires had decided to stay permanently in Argentina.
In 1955 he returned to Europe (Switzerland, West Germany).