This binocular design was invented by Alfred Baumann of Kölnische Straße 4, Cassel Germany in 1919. Baumann was operating as Optische Werke Alfred Baumann & Co in 1920.
The 4x Fata Morgana and 6x Optistar binoculars were believed also marketed by the firm August Fϋllgrabe of Cassel Germany (Kassel after 1926). Ninety years later, these binoculars still occasionally turn up in Germany, Holland, France, Austria, England, the USA, Switzerland, Ireland, Canada, Italy, Uruguay, Australia & New Zealand. These unique binoculars would have been well known to anyone in the optics trade in Germany at the time. The optics are really fairly good, especially for the time period. (By Mark Ohno http://www.miniaturebinoculars.com )