Horizontal Chainplates?

[Always Heelin]

Started noticing cracks along the fiberglass toe rail where the rear short stay chainplate comes through. After cutting out the crack to take a look at the chainplate, I noticed it was horizontal and only encapsulated between two layers of fiberglass. Is this a previous owner's creation or a normal chainplate on a 1969/70 26' Ericson?

I want to repair this the correct way. I've already been burnt by repairing things back to the way I've found them.