Metal Fatigue - Dinky Toys can suffer from damage known as metal fatigue. This is a factory defect, caused when lead and cadmium impurities in the casting metal react with the zinc alloy. It occurs most often in pre war toys, but can be found in later models. Signs of metal fatigue include warping, cracks and disintegration. It is not possible to reverse metal fatigue. Models with metal fatigue rarely have more than sentimental or some value for non fatigued parts.
Rebuilt toys - Rebuilt toys assembled from parts are much less collectible than toys in original condition. Watch out for parts with wear which is not even with the rest of the toy's condition, scratch marks around rivets, or excess amounts of glue. If the toy is held together with screws, be sure to purchase only from reputable dealers who will attest to an item's authenticity or supply a Certificate of Authenticity.
Repaints - Models are sometimes repainted which lowers their value compared to painted originals, check for signs of masking lines, or non original lettering or markings. Check to see that the age of the windows, tires and other parts matches the appearance of the paint coat. Also check for signs of over spray on the windows or in the wheel wells or other body areas.
Non original Packaging - Due to the value of original packaging or vehicles in original packaging, copies of packages are often produced. The original individual packaging should be made of cardboard from the time period, not laser printings on new, lighter colored card. Color coded dots on the ends of individual boxes should match the color of the vehicle inside. Check the interior of the box to see if there are any traces of the original paintwork which rubbed off.