Based on the serial number 103158 visible in the image, this Carl Zeiss Jena microscope was manufactured between 1921 and 1923.Records for Zeiss instruments from this era indicate that serial numbers in the 100,000 range were being produced during the early 1920s:Serial No. 92,422 is estimated to have been produced in 1922.Serial No. 183,073 (E series) was delivered in 1926.Your microscope features a classic "jug-handle" design. These robust instruments were standard for laboratory and research work during this period, often coming with a wooden carrying case and a set of interchangeable objectives. The key works the box lock and the lenses are in great shape