Strictly speaking chain plates are fixed to the hull vertically and the shrouds are attached to them at deck level. In Anne Marie’s case the chain plates are fixed under the deck spreading the load from the shrouds to the deck and hull.
Like most things in this boat time has caused damage. In this case rust. The two photos show what a bit of shot blasting followed by hot dip galvanising does. These will support the mast for another 40 years no trouble. Thank you Medway Galvanising