For example, I have sometimes referred to any angled-deck Essex/Ticonderoga-class* carrier as a 27 Charlie. The nickname comes from the SCB (Ship Characteristic Board) design number for a set of Essex-class carrier modifications that began to be defined in the late 1940s, when the Navy realized that a major upgrade program was needed to allow them to operate jets, which had to be launched and recovered at higher speeds, and larger attack aircraft.
While doing some fact checking for my Skyhawk book for Specialty Press, including trying to figure out why a hangar-deck illustration appeared to show two starboard deck edge elevators on an Essex-class carrier (see here), I discovered that I was in error. As it turns out, the SCB 27 modifications added more powerful catapults and arresting gear, a reinforced flight deck, larger centerline elevators with additional lift capability, a new island, and an increase in the aviation gasoline storage capacity, among other things, but not the angled deck or starboard deck edge elevator. The first nine modified were 27As with the new H-8 hydraulic catapult and the final six were 27Cs (hence the Charley nickname) with the even newer and more powerful C-11 steam catapult, the most significant difference between the two upgrades. The nine 27As and three of the six 27Cs were completed and placed into service as axial deck carriers; the addition of the angled deck was accomplished in a subsequent overhaul period. (Only one SCB 27 carrier, Lake Champlain, did not eventually receive the angled deck.)
Not, strictly speaking, a 27 Charlie (Kearsarge)
A 27 Charlie (Ticonderoga)
(Note that the shape of the forward elevator and the aft location of the starboard elevator mark it as a 27 Charlie but an Essex-class carrier with a rectangular forward elevator and the starboard elevator located more forward might also be one of the 27 Charlies.)
In short, of the 15 (including Antietam) Essex/Ticonderoga-class carriers with angled decks, there were only six 27 Charlies: Intrepid (CVA-11), Ticonderoga (CVA-14), Lexington (CVA-16), Hancock (CVA-19), Bon Homme Richard (CVA-31), and Shangri La (CVA-38).
The last three (Intrepid, Ticonderoga, and Hancock) of the six 27Cs modification were completed with the angled flight deck, so-called hurricane bow, and a starboard deck edge elevator replacing the aft centerline elevator. These modifications were the major part of SCB 125, which was then applied all but two of the carriers updated by SCB 27A and 27C. (These three were also unique in that the starboard deck edge elevator was located farther aft than on the other three 27Cs or any of the 27As subsequently modified in accordance with SCB 125, hence the hangar deck illustration mentioned above showing two locations for that elevator.)
The 27 Charlies are also distinguished by a 70-foot long forward elevator. However, the three modified at Puget Sound (Lexington, Hancock, and Shangri La) were originally completed with the standard SCB 27 54-foot forward elevator for some reason, with the 70-foot version being retrofitted at some point.
More than half of the angled-deck Essex-class carriers were therefore 27 Alphas plus the SCB 125 changes. One, Antietam (CVA-36), was neither a 27A or C but it was modified with an angled deck for an evaluation, which resulted in SCB 125. The starboard deck edge elevator was not incorporated. Antietam was eventually relegated to a training role.
Strictly speaking, it is not even correct that all angle-deck carriers with steam catapults were 27 Charlies. The first carrier to be modified in accordance with SCB 27A, Oriskany (CVA-34), had its hydraulic catapults replaced with steam catapults in the late 1950s when the angled deck was finally added to it. This was the unique SCB 125A configuration. From a capability standpoint, it was equivalent to the other 27 Charlies.
For much, much more on the subject of the development and description of U.S. Navy aircraft carriers, I recommend Dr. Norman Friedman's excellent U.S. Aircraft Carriers: An Illustrated Design History, Naval Institute Press, 1983, ISBN 0-87021-739-9.
* The most significant difference between the so-called Essex and Ticonderoga classes, if I understand correctly, is that the Ticonderoga-class had the upper part of the bow extended slightly to accommodate a second quad 40 mm cannon emplacement just in front of and below the flight deck. This gives rise to the categorization of short hull (Essex) versus long hull (Ticonderoga) ships; they were the same length at the waterline and the flight decks were essentially the same size.