I have both of these Hope Boxes, the three medal one, and the four medal one R4155 which is deeper, 11mm high and still 28mm wide. Both boxes seem to have the same number, so a, and b, should be applied.
Here is some terrible pics of the Waterloo Box 22mm wide and 5mm deep, the medals are 9mm wide. This is quite rare as boxes go.
Pics coming as soon as I can get them compressed.