- Deeds and other documents relating to property in the parish of Llansanffraid Glan Conwy and in Llanrwst, Denbighshire, 1835-1841. Also contains explanatory and genealogical material by R. Idloes Owen relating to the Roberts family mentioned in the Llansanffraid Glan Conwy deeds.
- Mathematics exercise book of William [Griffith] Williams of Llansanffraid Glan Conwy, 1835
- Photographs relating to Bangor history, 1896-1980's
- Copies of articles made by R. Idloes Owen relating to recusants in Wales and a history of Our Lady Immaculate Roman Catholic church in Bangor, 1985
- Copies of articles on various aspects of local history, especially the history of Bangor, by R. Idloes Owen. Material was published in the North Wales Chronicle, Country Quest, Gwynedd Roots, Window on Wales and The Universe