You likely have a set built between 1919 and 1930. If you go to this site (
The history of the telescope the binocular ) and scroll down (or search) to areas with Zeiss Binoculars, there are a number of files that have the information on runs. In my case, I looked at the Spreadsheet attached to the Zeiss Binocular Models entry, which , between lines 150 and 168, notes that binocs with the Lena logo were made from 1904 to 1945, and that serial numbers above 1 million began in 1919 and above 1,550,000 began in 1930, putting your pair in there more or less in the middle.
Cheers!
