If I had to guess I would think it was from pre Luis as I don't remember a large concrete structure at that location post Luis. The fact that it is now exposed shows how much beach erosion there has actually been. The single row of chairs was only directly in front of Rosie's but there was only about 15 feet between Rosie's and the five foot drop to the water. Also, I had never encountered rocks as I got into the water like I did three days ago. And it pretty much ran the length of the beach. Again demonstrating the significant beach erosion that has taken place.