Kindjal help needed

[Rivkin]

Here is the blade after FeCl etching. I've seen this structure many time but what is it - I have no idea. I thought it's tri-partite, but it's actually formed by 4 (2 at each side from the fuller) separation lines. All of these lines are actually 1-2 mm thick. You can see on the picture 3 such lines - 1 very close to the edge at the foreground, and other two surrounding the fuller. Is it tri-partite+hamon ???