PathOfGlory

Most gym leaders have a thing outside of the Gym Challenges; Milo has his farm, Nessa is a model, Piers is a musician, Bea has her karate training, etc.

Raihan is a dragon type trainer, and most dragon type trainers lean into the dragon hoard/treasure. In Raihan’s case it seems to be Hammerlocke Vault, where he not only keeps a wall of his trophies but also houses historical artifacts

It’s something he seems proud of, he’s happy to let people (with his permission and supervision) come in and look at what he has collected

And in the manga Rose and the others do know him as someone who does his research and does it well

His box set art card he is lounging in his vault reading a bunch of books most of which are even marked with notes

AND Hammerlocke’s Official Slogan is

“A city of great history, living and thriving within castle walls that date back to the middle ages."