You don't see the scale of the image. The line is 5/8 inch and the lower part of the cleat has two more attachments covered by the eye of the line. There are 4 through bolts about 1/4 inch holding them on.
I don't think you can order them. Gozzard has a few items of bronze that seem to be custom. The newer boats also have them in stainless as an option.
Here is the stem fitting: