Quiet as kept could be said a few different ways; quiet as it's kept, quiet is kept. The meaning is secrecy, to keep quiet, not volunteering or distributing information on certain relations. It's often an expression used in afairs where sensitive knowledge must be kept secret in order to avoid repraisals from other groups within the same society, culture, or subculture.
It was business as usual, quiet as kept.
The Urban Dictionary Mug
One side has the word, one side has the definition. Microwave and dishwasher safe. Lotsa space for your liquids.
Buy the mug