Situated in the toilet area of the building (when visited 2011), but possibly a former vestry, which would make sense of the text. The window is probably from the original glazing scheme of 1870.
Martin Crampin (ed.), Stained Glass in Wales Catalogue, University of Wales Centre for Advanced Welsh and Celtic Studies, Aberystwyth, 2018. https://stainedglass.delweddau.cymru/object/4691 (accessed 6 September 2025)