The eye detailing is made up of four roughly parallel main lines. From the top down, these are the brow line, the crease line, the upper eyeline and the lower eyeline.

On the dummy, the brow and crease lines are close together. There is then a broad space down to the upper and lower eyelines, which are again positioned close to each other. On the hero mask, the crease line is thicker and positioned lower. The upper eyeline is then located higher than on the dummy, leaving a distinctly larger gap before the lower eyeline.

This eyeline spacing is a standard technique used in make-up to give eyes a more open appearance. By contrast, the dummy eyes have been painted to represent Mr Sin "sleeping". The browhair brushstrokes are also bolder on the hero mask, giving the eyes a more alert and alive appearance.

If these paint variations were random, a third stand-by mask would be just as distinct in its own right. If deliberate, a stand-by mask would have been made as close a match as possible to the hero mask, due to its far greater prominence in the programme, rather than the dummy.

Close examination of the TV episodes revealed that the eye detailing on the 2008 mask is an exact match to the Mr Sin dummy. Once this was established, the identification of the piece as a stand-by mask started to look doubtful, and I realised other areas needed to be examined much more closely.