The Saladin consisted of a saucer section, and only a single nacelle. Each ship is similar in exterior design to that of a Constitution-class vessel of the 2260s. (Star Trek II: The Wrath of Khan; Star Trek III: The Search for Spock)
Ships of the class
The Saladin-class starship was a design originally created by Franz Joseph in his Star Fleet Technical Manual, which lists the USS Saladin as the prototype of the class. The production staff of Star Trek II: The Wrath of Khan and Star Trek III: The Search for Spock used some of the ships in the Technical Manual as background display images looped on monitor screens on the bridge.
According to the Star Fleet Technical Manual, the only difference between the Hermes-class scout vessel and her sister class, the Saladin-class destroyer, were her armaments and personnel. Where the Saladin-class housed three phaser banks and two photon torpedo launchers, the Hermes scout only housed one bank of two phasers, and the Saladin-class had a slightly bigger crew.
Intended to be merely background decoration, freeze frames and close examination have shown it likely (but not conclusively) that the images used were taken from the Joseph book with little or no modification. This was confirmed later by Rick Sternbach on a few occasions on TrekBBS.com's forums.
In the novel The Final Nexus, the USS Cochise (NCC-530) was a Saladin-class destroyer.
In the novel Dreadnought!, the USS Pompeii (NCC-424) was a Saladin-class destroyer.
The Saladin-class is also present in the Star Fleet Universe series of games. It served Starfleet for decades until supplanted by the Ortega-class war destroyer in the General War. The old destroyer shipyards were turned over to the construction of the Kearsarge-class light cruiser.
A nearly identical design is seen in Star Trek: Legacy, named the Apollo-class. The Apollo-class lacks the deflector/sensor dish found on the Saladin, as well as the "flush vent" details on the dorsal connection.