Dornier Merkur / Dornier Do B

The Dornier Merkur, also known as the Dornier Do B, was a single-engine monoplane passenger transport aircraft p in the 1920s, contributing to the development of passenger and cargo air transport in the decade following the end of the First World War.

The examples were used by various domestic and foreign airlines. These included the Swiss Ad Astra Aero, which operated two examples until 1925, when it merged with Balair to form Swissair, for many years Switzerland's national airline. source wikipedia