Not having the same unit but making a educated guess I would believeve your correct. If you have a meter I would see if the wires under the sink are the oposite ends of the wires where the battery goes. The second pair at the battery is either the main feed to the coach or possibly going to the power jack if so equipped.
The normal routing would be that the battery would join the univolt. There would also be a 110v line to the univolt. The 110 line may have been removed from the box for safety concerns since the univolt wasn't present.
The real concern is since those items were removed is if anything else has been removed or modified.
Now our 59 has 12v
and 110v lighting at every location but the back. My understanding is coaches of your vintage are all 12v
lighting and depend on the Univolt to power with on shore power. How are the currently getting 12v
without a Univolt? Or is the electrical box is actually the univolt and the power feeds to the battery were just removed?
The univolt does have fuses on one end and a distribution block. Pictures might help sombody with a simular vintage figure out what is going on.