Between 1153 and 1160, Orm son of Magnus & Warin his son were witnesses to this confirmation of earlier grants to the Abbey of Evesham. Despite appearances, this is not geographically misplaced, as Penwortham Priory was attached to the Abbey of Evesham in what is now Worcestershire.
Source: Lancs Pipe Rolls 1130 & 1155-1216 & Early Charters, Series V, Charter #IV p322-323_Farrer
Farrer comments at length on this and the following charter on pages 323-325 of the source cited above.
Between 1153 and 1160 (and apparently on the same occasion as the previous charter) Orm son of Magnus & Warin his son were witnesses to a grant which dovetails with Charter #IV above. The other witnesses - or at least those named - were identical for both charters.
Source: Lancs Pipe Rolls 1130 & 1155-1216 & Early Charters, Series V, Charter #V p325-326_Farrer
This undated but otherwise identical version of the above is recorded as Charter #XXXV in the Werden MSS.
The dating of such charters is usually an editorial addition, based on the known dates of the parties involved and/or the witnesses, or other historical events.