According to the script for "Author, Author", this type of vessel was identified as a "small ore carrier".
Viewscreen of the Norkova
Bridge of the Norkova
Viewscreen of the Xhosa
Bridge of the Xhosa
According to the final draft script of "For the Cause", "The Bridge is laid out in a rectangular design than the circular pattern preferred by Starfleet. The rectangle runs fore and aft, with the forward end dominated by a viewscreen and the aft by a doorway. The helm control is in the center of the room and the other consoles line the two opposing walls and are usually unmanned. This is definitely a "working" ship with no frills. This is also an older vessel and should not have the clean, freshly scrubbed feeling of a Starfleet bridge." 
In "For the Cause," the Xhosa's bridge set was built on Paramount Stage 18, and was built in part from the bridge of the USS Saratoga. In designing the bridge, the Art Department took a cue from a reference in "Family Business", as according to Scenic Art Assistant James Van Over, "There had been references about how the Xhosa was an old ship, so we mimicked the old blinking lights from the original series on the ship's control panels. [Scenic Artist] Doug Drexler and Mike Okuda made me watch episodes of Star Trek over and over again to make sure the timing was right on how they blink." (Star Trek: Deep Space Nine Companion (p. 341)) Alternatively, display graphics were patterned after the screens seen on the bridge of the USS Enterprise in the original series. (Star Trek Encyclopedia (2nd ed., p. 568))
The Star Trek Encyclopedia (3rd ed., p. 14) speculated that various reuses of the Batris studio models were all Antares-class ships, used by different species, and that the Antares (which went unseen in "Charlie X") might be of the same design. A different Antares-type design would later be introduced as part of the TOS remaster.