Lombard and breast fat have to deal with the yield. When the stamp is KL, the lombard and kidney fat is intact. The Yield Grade and supply determine prices to a great extent. Lack of oxygen in the muscle would turn the meat sour. Aging breaks up the tissues of the muscle, making the meat more tender.
Proper conditions are necessary.
There are two possible types. Dries out the meat, no moisture, not an even distribution of air. The use of ultraviolet light is recommended Time to dry - age will greatly depends on temperature and size of item to be aged. Full quarter, 4-6 weeks, ribs, strip loin, tenderloin somewhat less. Do not age any wrapped meat.