I am old enough to know and have work with wooden hatches, king beams and sister beams and canvas covers on coasters and barges. The hatch batten's could be both wood or steel, though steel ones were easier to use, because they were thinner and easier to work in between the cloths and clip. Remember the thick edge of the wedge always points to where the sea comes in board, with a single hatch you start from forward to aft with the thick end pointing forward and then amidships to aft the thick usually point aft. Same principle on the head ledges. Then lashings or battens across the hatch to secure the cloths in the event the battens and wedges come loose. If the hatch coamings are rounded on the corners then they would certainly be steel.