The base beneath the box is quite substantial, provided there is internal bracing inside the box. To my eye, the whole is timber. Raising a wooden box off the deck is good practice to prevent a "water sandwich" which results in rapid deterioration of the wood. The base gives air circulation to keep the timber dry so rot is inhibited.
Placing the box against the cabin wall allowed firm attachment. This reduced the need for an extensive base arrangement. And, it kept the box out of the way of passengers and crew.
Although it tells nothing about the use of the box, the shape of the base indicates the maker was a craftsman. Note the "toe kick" area is cut out, but done with a eye-sweet sweeping curve.
Two different size "pipes" or "conduits" is not surprising. The section coming through the deck was likely installed prior to fitting the box. At that time, the pipe was found too short and an extension installed. The mechanic used what he had at hand to get the job done.
The clip holding the pipe to the box appears to be unpainted. Perhaps it was installed last minute? perhaps under way?
The trim around the top of the box would have been a water trap and invited deterioration. It would have been installed only if necessary for the object to serve its purpose. One possibility is a fiddle to keep objects on top from rolling off. I doubt that was the case. Or, more likely, the trim pieces may indicate that the top is really a lift-off lid of some sort.
There are two "mystery boxes" on Titanic. This one, and another at the front of B deck. The one forward was obviously inset into a rail opening intended for the starboard ladder down to the well deck. It is neatly balanced with the port ladder, which remains. I've often wondered if these two mystery boxes are related because they are located where each has a full view of its respective end of the ship.
Then again, the boxes may just have been storage for the anchor bearing grease or soap for prop wash. Who knows?
-- David G. Brown