It looks like a crack of some kind, but I've never seen one like it. Every die crack I've seen on older Canadian coinage start at a specific section in the design that has a sharp change of direction, That is usually from a denticle, a bead, a serif on a number or letter, or something in the portrait or reverse design where there is a sudden change of direction. That creates a tremendous stress point during striking so the metal will crack ... too much force on a small sliver/section of the die.. Your inset goes from smooth to smooth, so I don't understand, unless it didn't happen during the strike, but rather when the 2 components were combined and didn't quite match. It's a keepr since no one else on here has shown one.