Within the framework of Art. 123(2) and Art. 82, Rule 137(5), first sentence, should be construed as permitting any limitation of searched subject-matter which is unitary with the originally claimed subject-matter, irrespective of whether the technical feature(s) used for the limitation has/have been searched.
Rule 137(5), first sentence
For Euro-PCT applications where the EPO acted as ISA or as SISA, the examining division has to issue an invitation under Rule 164(2) for any now claimed but unsearched invention contained in the originally filed application documents (description, claims and drawings, if any) which are to serve as the basis for examination upon expiry of the six-month time limit set in the communication under Rule 161 or Rule 162 (see C‑III, 2.3).