Leg banding is generally not standardized, subject to the whims and coding of breeders. Best course of action is to seek out bird clubs or breeders if you know general time frame and place of hatching.
CTP is one I’ve seen asked about before, and I believe it was MI not M3 on that one - it was also on a conure. Not sure where you are located, but if you are in or close to Michigan it may be “MI” (birds also move around from state to state).
There is no central registry for leg bands, so it’s pretty hard to guess the breeder. It could be Parrot's Talking owned by Todd Cotterman (Michigan) - which I don’t believe is in business anymore. CTP could stand for Cotterman's Talking Parrots? I believe there is/was a group on Yahoo that researched leg bands if you wanted to dig into it more.