Hi Ed,
I was on the USCGC White Pine for a couple days in '97 (serving as a stand-in Officer of the Deck (OOD)), and also was on the USCGC Sweetgum (WLB 309). The hatches in the buoy deck that lead to the stores below are a one-piece hatch bolted down, then lifted out using the ship's crane. There is, at each corner of the hatch, at least a recessed padeye that you would run a line or cable through, then lift the hatch up. I don't remember if there was also one link of chain at each padeye or not, but it was definitely recessed (so you don't trip and kill yourself doing buoy ops on deck). The hatch would be moved out of the way, then extra sinkers (the large cement blocks used to keep the buoy from drifting too far) could be stored there. On the Sweetgum, we had at least one down in the hold, but more for a better ride and an emergency spare than anything. I don't believe we opened that hatch in the two years I was onboard.
Your boat looks great. It brings back a lot of great memories. One of the neat things about the White Pine is that, unlike most of the other ships in the class, she had spuds so you could drop them into the mud and become a moored boat.
Hope this helps.
George Borlase