My horse, Slick, is a double registered Missouri Fox Trooter/ Spotted Saddle Horse. He is the most lovable, wonderful horse you could ever imagine. His gaits are to die for...you really don't even move in the saddle. He is extremely smart with strong hooves that have NEVER been shod. He was a Halter Horse in his previous days, did Elk hunts for several years, then did Showmanship for a while. He did all of that with no shoes at all. They are known for their great feet. I'm describing him because he is the apitome of a Spotted Saddle horse....you just can't go wrong with them! (Well, maybe you could but I haven't seen a bad one yet!)
I think the registry was started by the Kentucky Mountain Saddle Horse Ass. For horses with too much white markings to be registered with them. This was taken from the KMSHA/SMHA web site for breed standards.
KMSHA horses can be any solid body color. White markings should be limited to the face, (no bald faces) the legs (no excessive amount of white above the knees or hocks) and an area on the belly that is behind the breast bone and under the ends of the rib cage not to exceed 36 square inches (6x6 - no bigger than the size of the hand).
Any horse that does not meet the limited amount of white requirement as stated above but carries significant white markings known as tobiano, overo, sabino, etc. may be registered/certified SMHA, (a subsidiary of the KMSHA). A colt or a filly that is of solid body color and is foaled by one or both Spotted Mountain Horse parents, must be registered SMHA with no exceptions. At this time, there is not a fool proof genetic test that can determine that a solid colored offspring will not throw spots. A solid colored gelding from a Spotted parent(s), may be registered/certified either SMHA or KMSHA, but not both.
So basicly its a KMSH with excessive white markings.