In T 634/91 the claimed prior public use consisted of the presentation of a circular saw at an opponent's place of business during a meeting between the patent proprietor and a potential buyer. Without elucidating further, but referring to the decision in T 830/90 (OJ 1994, 713), the board held that such talks constituted a tacit understanding to maintain secrecy.
In T 292/93, the board ruled that a demonstration conducted for a small group of potential customers on the premises of a company with close links to the opponent was inconsistent with the existence of an obligation to maintain secrecy.
In case T 478/99 a demonstration was made by two potential clients. It could not be proven that a confidentiality agreement existed. The board held that the sole absence of an explicit request for confidentiality was not sufficient to conclude that there was no confidentiality, because secrecy may result from an ethical code of conduct for the employees of big companies such as the two clients in question. Consequently, the board considered the alleged public prior use not to be proven.
In T 823/93, according to the board, the development of a new apparatus is usually kept secret from competitors. In the case at issue, the development of the apparatus had to be regarded as the result of co-operation between the opponent and the client. The board therefore took the view that, on the basis of these facts, it could be assumed that none of the parties had an interest in disclosing any information about the apparatus and it was likely that the technical reports exchanged between the parties were tacitly required to be treated as confidential. The board also held that the general conditions of business, which had become the conditions of contract and required the plans, designs and other documents to be handled confidentially, also extended to verbal information and details given during the presentation of the apparatus. In these circumstances, the board decided that the employees to whom the apparatus had been presented could not be considered as members of the public within the meaning of Art. 54(2) EPC 1973.