Several problems commonly affect mandolins in general and specifically Ibanez mandolins. The list below should help you evaluate the condition of a vintage Ibanez mandolin.
Top and Back Cracks
Like any mandolin, vintage Ibanez models can suffer from cracks in the top and back. The solid spruce top, and less commonly, the solid maple back, can split from the stresses on the instrument or rough handling. Cracks often start at the f-holes and run parallel to the grain. In most cases, a short crack is a simple repair that can be fixed by a professional luthier with glue and/or cleats.
The issue of binding rot is more specific to Ibanez mandolins and could be related to the aging of the plastics used for the binding material. Keeping the mandolin in the case, with no air ventilation, may contribute to the breakdown of the binding. In the early stages you will see splotches of rust and brown color over the normally cream-colored binding. As the binding rot advances, the plastic seems to dry out and chunks of binding can break away, often at the points where a bump can break the rotten binding loose.
Another binding-related problem happens at the joints of the sides (rims) and top/back. The plastic binding can shrink over time and pull away from the wood, leaving small gaps along the edges of the mandolin where binding meets wood. Check especially in the areas of the scroll and the endpin for black lines along the binding edge. Run your fingernail along the edge and you may feel a small gap there. In most cases this is not really a structural issue, as only the binding is affected and the wood is kept in place by the kerfing joints inside.
Headstock Overlay Deterioration
524, 524AV, and 524CW models feature a faux tortoiseshell overlay made from plastic. Over time, this plastic can dry out, crystallize, and crack. Again, poor ventilation from extended periods in the case is probably the cause of this problem. Look for cracking and spidering in the headstock overlay, especially around the tuner holes and truss rod cover screw holes.
Ibanez pickguards are made from the same faux tortoiseshell plastic as the headstock overlay. If left off the mandolin for an extended period of time, the pickguard may warp and shrink, and no longer fit correctly when you try to reattach it. If you leave the pickguard on the mandolin, and keep it sealed in the case for a very long time, the plastic can release gasses which will damage the finish and binding it comes in contact with.
Many of these problems relate to proper storage of the mandolin. Too much time (months and years) in the case with no ventilation can lead to damage of the delicate plastics. Storage in a well-ventilated area of appropriate humidity will prolong the life of the binding and plastic parts. With proper storage you can stop the progress of deterioration, and stabilize the condition of your mandolin. Ibanez mandolins with binding shrinkage or plastic breakdown can still be structurally sound and worthwhile instruments.