You could ask the appy association.
There are not that many registered appy breeders.
If that is what your horse is, they may know who uses that brand and brands in the jaw.
Looks like a rocking 5 R.
I don’t know anyone that brands their ranch brand in the jaw as that one seems to be?
Ranch brands generally are somewhere in the main body.
Jaw and butt brands are for other than ranch brand id.
Most jaw brands are for breeding numbers or in specific cases, for quarantine/condemned stock under observation.
Being such a different brand and brand use as branded, I expect if you get the word around, someone may know where he came from.
You are sure he is an appy?