Found these snapshots.
From 1975!
A stand-up or kneeboard. It was very loose, if I remember.
4’8’’ x 19-1/4". It was a stripped-glass re-shape. One of my first boards. Did the glassing as well. I was, maybe, 15.
[img_assist|nid=1048155|title=4'8'' tri fin|desc=|link=none|align=left|width=204|height=640]