A brass, slightly larger than the others listed, 'one dog' opening porthole. One has the legends L then an admiralty arrow and C to one side as shown in the images, along with a few serial numbers, the other different legends.
Measures 29cm total diameter and the glass is 17.5cm.
Weighs a little over 5 kilos each.
I have 2 of these available and they aren't as shiny now as in the images!
Will easily polish up.