Many breeds have a double coat (2 different layers, both an undercoat and an overcoat). This breed however, has 1 single layer of growth, similar to humans.
A quality dog that is well-groomed will have a coat that has a very deep shine to it. Each strand will be plump with moisture, which when blended together makes for a lovely, silky coat. In fact, when outside in the sunlight, it can look almost metallic due to intense shine. This is one reason why the blue in the coloring of the coat is often referred to as metallic blue.
Now, with this being said, not all will have this type of coat. Long, silky, soft strands that are almost reflective is the desired AKC standard….Due to genetic throwback genes, this is not always the result. There are many pet Yorkies that will have a thicker coat…and some may appear to be double coated.
Some will have a more wiry coat... it will not fall smooth. This is not a desired trait, but it does occur from time to time. For those with wiry textures, full show dog length will not be achievable...A puppy-cut style and trim is highly recommended.