John - a look at the Geograph website shows that the site of Killough station near Ardglass, on the East coast of Ireland, is now a caravan site. In a couple of pictures (see http://www.geograph.org.uk/browse.php?p=437936
) there is a glimpse of the end of a building that might be the building behind the box. Note too the gas cylinder and rack by it - this might indicate a possible solution to your query?
The other two possibilities don't bring up any relevant pictures, but Ireland has far fewer pictures on Geograph than other parts of the UK/Eire.