Deck Plates (Vent Plates)

The items shown on the main deck were ventilation plates for exhausting the engine fumes from the tank deck when loading those tanks or other motorized equipment. All early LSTs built had these installed. I believe through the 542 class.

This was not a good ventilation system and was changed to a system of large electrically operated ventilation ducts later on, and the main deck vents removed. All it took was one Amtrak running over one of those vents and it was pretty much useless.

Also an additional layer of steel was placed on the main deck later to facilitate handling the heavier tanks.