Philips Mullard Resources
Mullard Point Contact Diodes
These two articles, courtesy of Jon Evans scanned from the Mullard publication Outlook indicate that the development of early point contact diodes such as the OA60 and OA61 were in development from 1952.
See main article on the History of Philips Semiconductors in the 1950s
Above: Germanium Crystals Outlook October 1952
Above: Mullard Germanium Diodes Outlook January 1954