Did a bit more delving. My initial thoughts on it being an "oddball" were based on the fact that windows with curved tops and square-cornered bottom corners were the stuff of the MGWR and, on some stock, CBSCR.
The side curvature and beading is most in-MGWR-like. The height of the windows, and the side curvature are not very West Cork-like, either.
The W & T don't appear to have had carriages of this window design - the above vehicle has comparatively wide window panes for an old coach. That COULD suggest a Tramore vehicle, but none of them as far as I am aware had curved tops and square (ouch!) bottoms, nor did they have any sort of beading or ventilators like the yoke above.
I tried to find decent shots of Macroom coaches this evening to compare, but there's so little to be seen on that line. However, the beading certainly reminds me of a photo I've seen somewhere in the past, as does the side profile, and the ventilators above the doors appear to be of that type.
In the absence of anything else, I'll stick with my initial hunch that it's from the Cork & Macroom Direct Railway. I would be interested to know more.
I should add that all of the above is on the presumption that it is clearly of the 5'3" gauge. What width is it? Is there and end view of it?
If it turns out that it's narrow gauge, we've another issue entirely on our hands; with Cork & Muskerry Railway being the most likely contender. I'm not sure it IS narrow-gauge, though.