Double breasted or center fastening?

[PMBardunias]

Only,this raised chest cover can be achieved also with overlapping. The belly part would be double and the chest would only be one layer

I agree that it can be done that way, but it clearly is not being done that way in the image I posted. As to Patroclus, his armor is far different. The scallop at the neck is needed because the central portion is too high without it, cutting into the neck. The high front is quite clear on that vase, as is the fact that it is one layer showing.

There are images that don't show the raised front, but usually they are poor quality renders. One example of a good artist appearing to make this mistake is the famous Douris arming scene. The fellow who appears to be fastening the tube in front also lacks a high front while the other images on the same vase all have ornate upper chest sections.