The class A uniform is the equivalent of a business suit. A good rule of thumb is that you would wear a class A to a function where a civilian would wear a business suit.

"Full dress" (however you describe that, such as white gloves, shoulder cords, etc.) is the class A worn for ceremonies, parades and such. For "formal dress" (where a civilian would wear a tuxedo), the class A can be worn with a formal shirt and bow tie.

How did a terminated member happen to have a department uniform, anyway? Shouldn't it (and all other accouterments) have been retrieved when the employee was terminated?