|The USS Cortez from Star Trek: The Early Voyages issues #5-6.|
I think there was a lot of speculation in the Trek community after The Wrath of Khan about whether the Miranda-class was in service during The Original Series and if so, what did it look like? Unfortunately, the comics - like everything else except the TV shows and movies - aren't canon, so it's a moot point. That's probably the one thing I don't like about the Trek franchise, Paramount's canon policy..
(Picture via Memory Beta, the non-canon Star Trek Wiki)