Hereafter a brief summary of the background to G 1/93.
In T 384/91 (OJ 1994, 169) the question was referred to the Enlarged Board whether, given the requirements of Art. 123(2) and (3) EPC 1973, a patent could be maintained in opposition proceedings if its subject-matter extended beyond the content of the application as filed, whilst at the same time the added feature limited its scope of protection. The conflict here was that the "limiting extension" had to be deleted as a breach of Art. 123(2) EPC 1973, but to do so would broaden the scope of the patent and thus contravene Art. 123(3) EPC 1973 (see G 1/93, OJ 1994, 541).
This problem was extensively discussed for the first time in T 231/89 (OJ 1993, 13). In this decision, an additional, limiting feature was added to the claim during grant proceedings. The opposition division revoked the patent on the grounds that the feature had not been disclosed in the application as originally filed but its deletion would contravene Art. 123(3) EPC 1973. The board of appeal held it to be inappropriate to take Art. 123(2) and 123(3) EPC 1973 as independent of each other while applying them in conjunction to revoke the patent. This "paradoxical result" could be avoided by interpreting the two paragraphs in terms of their mutual relationship, where one was predominant, i.e. independent, and the other subordinate, i.e. dependent:
(b) If Art. 123(3) EPC 1973 was to be taken as independent, the added feature could remain.
If the limiting feature was irrelevant for novelty and inventive step, it seemed reasonable to opt for alternative (b); protection of third parties was then crucial. If, on the other hand - as was the case here - the added feature had no technical significance, then alternative (a) seemed appropriate and, thus, the deletion of the feature justified.
In T 10/91 a neutral feature of no particular value for the skilled person was added during the examination proceedings. The feature had no technical significance. It could therefore stay in the claim, but could not be taken as delimiting when examining for novelty and inventive step.
In T 938/90, however, the addition was technically significant and it had to be taken into account in the examination for novelty and inventive step. The board therefore declined to apply the principles developed in T 231/89 and dismissed the patent proprietor's appeal against the revocation of the patent (see T 493/93).