Mid-North NJ and it was constructed in the mid 1980s. There is a floor above and the deck thickness is about 2". We tried to get into an existing core to get the overall depth but a plug did not allow us to get the final depth; we are estimating 4" total thickness (2" deck; 2" topping; fire rating N/A due to the fireproofing) based on what information we could grab. Some additional information is this is an office building and the deck spans 10'-0".
djl5596,
Check out this older Inryco Deck Catalog. Not sure if this is what you actually have but it shows how some cells are covered with a bottom cover plate to provide runs for electrical lines, etc.
This is a 1973 catalog so a bit earlier than your building.
I think this is what you have - some combination of open and covered deck.