A press for producing light building (hard fibre) boards was installed in a factory shed. Although the door bore the notice "Unauthorised persons not admitted", customers (in particular dealers in building materials and clients who were interested in purchasing light building boards) were given the opportunity of seeing the press although no form of demonstration or explanation was given. An obligation to secrecy was not imposed as, according to witnesses, the company did not consider such visitors as a possible source of competition. These visitors were not genuine specialists, i.e. they did not manufacture such boards or presses, but were not entirely laymen either. In view of the simple construction of the press, the essential features of the invention concerned were bound to be evident to anyone observing it. There was therefore a possibility that these customers, and in particular the dealers in building materials, would recognise these essential features of the press and, as they were not bound to secrecy, they would be free to communicate this information to others.