Gemsmith’s tools, an obscene amount of jewelry.
He’s short, even for a gnome, and tends to have a mildly crazed expression, unless discussing jewelry, when he looks obsessed.
Sinnameron is a master gemsmith. One would be hard pressed to find an artesian better than he. The fact that he is mad is a small price to pay.
He had always had an affinity for gems and jewelry making, and proved to be a natural at creating enchanted jewelry. He made several fine pieces, including the necklace Cat’s Eyes as a favor to a friend. His greatest achievement was the fabled set of Stones of Sinnameron. But, never very stable to begin with, Sinnameron became obsessed with gems, and eventually went completely mad. He lives as a hermit now, constantly tinkering with his tools and stones.
Sinnameron seems only mildly insane until the conversation turns to gems (which he will endevor to do), when the depths of his madness become apparent.
He would be a fine source for any enchanted jewelry, only he is not willing to part with anything. He would have to be tricked or coerced, or stolen from.
Use caution if getting him to identify something. You might not get it back.
He might ask the PCs to go find some rare gem for him, because he is getting too old to go hunt them down anymore. (Although there is some speculation that he might be nigh immortal, as the result of one of his earlier projects.) Whether or not he follows through on payment is another matter entirely.
He would be willing to buy any type of jewelry or gems the PCs come across. He might even try to steal it.