Art. 115, first sentence, EPC states that any third party may present observations. There is no requirement to state whether the third party is acting in its own name or on behalf of someone else (T 1224/09).

In T 811/90, the patentee had filed an appeal against a decision of the opposition division concerning the removal of certain documents from the public part of the file. The opponent was not a party to the impugned decision and was consequently not entitled to be a party to the proceedings before the board. His request was therefore inadmissible but was admitted as an observation by a "third party".

Similarly the board in T 446/95 held that the intervention of a company was inadmissible, so its auxiliary requests were also inadmissible. However, there was nothing to prevent the company's observations and the documents it had filed from being dealt with under Art. 115 EPC 1973 (T 223/11).

In T 7/07, the board agreed with the findings in T 1196/08 that an intervention based on proceedings for infringement of a patent that has effect in a particular state solely on the basis of national law is inadmissible. The intervener's submissions were consequently regarded as third-party observations under Art. 115 EPC.

In T 887/04 of 14 November 2006 date: 2006-11-14, the board found that, although the intervention had to be held inadmissible, account had to be taken of document D5 cited by the intervener under Art. 115 EPC 1973 for the purposes of examining novelty and inventive step, because, despite its belated submission, it was highly relevant.