T. Ertel & Sohn
founded 1834
"Traugott Leberect Ertel (1778-1858) joined the Mathematical-Mechanical Workshop in Munich around 1812 and became its sole proprietor around 1820... In 1834, Georg Ertel (1813-1863) was made partner and the firm began trading as Ertel & Sohn." The company manufacured scientific instruments.