Model of a Caisson in its Bed

Framed model of a ship's door with double keel, placed in the sponsons of a dry dock. On one side the ship's door is fully finished, the other side open. Parts of the three decks, connected by stairs, can be removed; inside a division into compartments. Two small scuppers at the bottom of the closed side; their operation is unclear, but seems to be done with wedge-shaped shutters. Only one pump on each side. The opening of the dry dock has three sponsons, so the ship's door can be set in two places.