BB-35 USS Texas had started life with "casemated" 5"51 on the second deck. They were fitted out with the metal shutters and portholes, as they backed up into various compartments. I want to remember that they were as tin as 1/8", but that could be faulty memory.
They were not water-tight and a real source of annoyance. So, spanning 4 separate refits, they were all moved up to the Main deck as part of the superstructure.
To my knowledge, once part of the "main castle" they do not appear to have ever had weather protection.
There may have been provision for a canvas dodger, outboard, but I never saw a sign of it on any of my in-person visits.
All of which invites me to wonder about Arizona, built well afer Texas, and using lessons learned from previous ships.