Thank you Ronald. However, the main issue is that the tang is broken about 1cm inside the hull. So the tang disappears inside the hull and I have no idea about the tang shape and I do not know where it is fixed inside the hull.
Sailinghoutx put some pictures of the broken tang on a dropbox:
https://www.dropbox.com/sh/hi28arvy38eqn4p/7NkMJQUzEKMine is broken almost the same way.
Pierre