I've been doing some research after a discussion in another thread. The Rocky Mountain horse association does hold the registered trademark of the breed. I assume this is why they are the only Old Tobe line horses recognized as a breed.
The RMHA was formed first but because of disagreements in breed standards the KMSHA was formed and after that the SMHA.
The KMSHA only allows registration of a foal from parents in which at least one of them is certified KMSH
The RMHA on the other hand only allows registration to foals born where both parents are RMH Both certified parents, either rocky, kentucky or spotted must be, through DNA, traceable to the foundation stallion.
Neither the RMH and KMSH can have excessive white markings. The KMSHA started the registry of the spotted horse so those born with the correct parentage but the wrong coloring could be registered.
I'm pretty sure this is all correct, if there is someone from the office of either registry who reads this and finds a discrepancy feel free to correct me