I usually use numbers as class names, following an internal code. One such example is:
Project 4006a-class Missile Cruiser.
The first number represents the ship type, with 1 being FACs, 2 being Frigates, 3 is for Destroyers, 4 is Light cruisers and so on. The ship type represents more a size-range instead of a role, with a survey frigate receiving the "2" designation, despite not being a combatant.
The second number is always a 0, functioning basically as a separator.
The third and fourth numbers are representative of which iteration this design represents, the example given being the 6th Light Cruiser design since the start of the game. It does not represents the generation of the ship (a new generation happens every time there is a new engine). In this case, the 4006a CGs are in the same generation (Magneto-Plasma) of the 4005 Jump Cruisers.
The letter represents refits of the class, following alphabetical order, so the "a" is the first refit of this particular class.