In the period that followed G 2/98 (OJ 2001, 413), the above-mentioned proviso of the Enlarged Board in respect of generic "OR" claims gave rise to divergences in the jurisprudence of the boards. These led to a further ruling by the Enlarged Board in G 1/15 (OJ 2017, A82); see also chapter II.D.5.3.2 below).

In some of those cases, subject-matter disclosed in the priority document and falling within the generically formulated claim of the subsequent European application was denied (partial) priority because the terms of the proviso were found not to be met. Such approach could sometimes lead to a "collision" under Art. 54(3) EPC with another member of the same European patent family (particularly in situations involving what is sometimes referred to as a "toxic priority" or "poisonous divisional" – see also T 557/13 of 17 July 2015 date: 2015-07-17, OJ 2016, A87, summarised in the next section). In G 1/15 (OJ 2017, A82), the Enlarged Board observed that in a number of decisions the words of the proviso had been understood as a further test to be complied with for a claim to partial priority to be accepted, an interpretation which the Enlarged Board rejected. Accordingly, G 1/15 has overruled the approach taken in T 1127/00, T 1443/05, T 1877/08, T 476/09, and other decisions mentioned in G 1/15, point 2.2 of the Reasons.

However, other decisions issued after G 2/98 acknowledged partial priority in comparable circumstances.

Thus, in T 665/00, the board found that the subject-matter of an alleged public prior use within the priority interval was described in the priority document and also fell within the scope of the claims of the disputed patent, but that the priority document did not necessarily describe all the subject-matters claimed. Referring to Art. 88(3) EPC 1973 and G 2/98 (OJ 2001, 413), the board held that different elements of a patent application could enjoy different priority dates and that this was also applicable to a single claim encompassing alternatives and being, thus, separable into a plurality of subject-matters. Of the different alternatives contained in claim 10 (relating to a powder containing hollow microspheres the specific mass of which was described by the generic term "less than 0.1 g/cm³"), the non-compacted powders containing "Expancel DE" microspheres were covered by the claimed date of priority. The claimed prior use, which came after the priority date and involved a product containing the same "Expancel DE" microspheres, could therefore not be novelty-destroying. See also T 135/01.

The meaning of the proviso of G 2/98 in relation to the "OR" claim situation was the subject of extensive obiter remarks in T 1222/11. According to the board, the condition "provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters" should be given a different meaning from that attributed to it in T 1877/08, T 476/09, T 1443/05 and T 1127/00. This condition could not be meant to set out the manner in which the subject-matter of the "OR" claim must be defined. This would, at least in relation to generic terms, be at variance with the disclosure test based on the principle of an unambiguous and direct disclosure (cf. G 3/89, OJ 1993, 117). For the purpose of the assessment required by Art. 88(3) EPC, the board considered that the wording of the above condition referred to the ability to conceptually identify, by comparison of the claimed subject-matter of the "OR" claim with the disclosure of the multiple priority documents, a limited number of clearly defined alternative subject-matters to which the multiple rights of priority claimed could be attributed or not (cf. examples in the Memorandum drawn up by FICPI (M/48/I, Section C) for the Munich Diplomatic Conference in 1973, as cited in G 2/98).

T 571/10 expressly applied the approach of T 1222/11. The application in suit, which concerned a pharmaceutical composition, and D9, also a European application, shared the same filing date and claimed priority from the same earlier national application. By comparing the generic subject-matter of claim 1 in issue with the priority document, the board identified two clearly defined alternative subject-matters (a) and (b) as being encompassed by the claim, but not spelt out in it. Only alternative (a) was fully disclosed in the priority document and therefore enjoyed the claimed priority. D9 could belong to the state of the art under Art. 54(3) EPC only in so far as the priority of the application in suit was not validly claimed while the priority of D9 was. For alternative (a) of claim 1, this was not the case, since D9 had no valid earlier effective date. For alternative (b) of claim 1, D9 was state of the art under Art. 54(3) EPC only for the subject-matter for which the priority claimed for D9 was valid, which was that of alternative (a). This subject-matter was not novelty-destroying for the subject-matter of alternative (b) of claim 1, as it had no overlap with the latter.

The decision headnote states: "In a case in which a single priority is claimed for a given application and a number of features of a claim of said application are generalisations of specific features disclosed in the priority document, a partial priority is to be acknowledged, as long as it is possible to conceptually identify, by a comparison of the claimed subject-matter with the disclosure of the priority document, a limited number of clearly defined alternative subject-matters, including among the alternatives the specific embodiments which are directly and unambiguously derivable from the priority document. In order for this condition to be met, it is not necessary that the clearly defined alternative subject-matters are spelt out as such in the application, nor that the word "or" actually occurs. This condition extends to the case of multiple priorities. In that case, a comparison with the disclosure of each of the priority documents is necessary and for each of the clearly defined alternative subject-matters the earliest priority from which the alternative subject-matter is directly and unambiguously derivable is acknowledged."