No such thing as a Miniature Cocker Spaniel is acknowledged by AKC....there are 2 types of Cockers: American Cockers and English Cockers. Americans are a smaller breed than English, but not "miniature" in any way, unless just happen to be the runt of a litter. Of course, there are breeders who are adding "miniature" on everything from Yorkshire Terriers to Boxers to try to make money off of a buyer. New 'breeds' spring up all of the time to fill some type of desire for something 'special'...it doesn't make them a real or acknowleged breed at all.
Is this a dog that you are considering obtaining? If it is, think of it soley for a family pet and have its health checked out, then enjoy the dog for what it is. But it is certainly not anything that would be showable or legitimately bred from.
regards,
toodles