ISS
ISS, short for Imperial Star Ship, was the prefix designation given to space-faring ships in the Terran Empire registry and in the Terran Resistance Forces in the mirror universe. ()

The use of ISS as a prefix for Imperial ships was already in use by the 22nd century, where ships of the  were designated with the ISS prefix. ()
 
 

The Terran Empire was still using the ISS prefix for starships in the 23rd century. (; )
 
 
 
 
 
 

After the fall of the Terran Empire to the Klingon-Cardassian Alliance, the use of the ISS prefix wasn't used on vessels like the Terran raider, but was resumed when the Terran Rebellion built a  starship based on specifications "acquired" from the prime universe. ()
 
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