It is actually the zoomed in gap between the watch glass and the metal bezel. The light blue "sealant" area is actually the edge of the glass which has been microscopically chipped through wear, and is at a slight angle so as to be visible...
Well Eagle, Ceathreamhnan and Knighty got it right. Score wise Im thinking the following:
Eagle: +3 for getting it right and being the first
Ceathreamhnan: +2 for getting it right and stating the part first (would have got +5 if you had pinpointed where abouts!)
Knighty: +1 for getting it right
Bigsoy: -1 for getting it wrong
Clocked: -1
Sam: -1
Mark: -1
White Giant: -1
Alien8: -3 for getting all 3 suggestions wrong!
Suggestions before continuing? Its going to be hard to find things that are abstract enough I think!