Painting roller kit (un-used) (East Hendred OX12)

This is a small painting roller kit with some sort of edge device which flicks round to the end of the roller, presumably to help paint into corners to avoid the end of the roller smearing the adjacent wall. There is a button on the yellow handle which rotates the arm holding the black 'shield' by 90 degrees to avoid the end of the roller touching anything. I only presume because it has never been used. The back of the box is slightly discoloured.