What started as a hobby and grew into a small business for Nate Sanders has turned into a multimillion-dollar enterprise with a literary – and royal – pedigree.

Sanders’ company, West L.A. auction house Nate D. Sanders Inc., this week will sell two handwritten poems by “The Great Gatsby” author F. Scott Fitzgerald and a 540-year-old document signed by King Richard III.

They’re just the latest high-profile items to be auctioned off by Sanders, who started collecting celebrity autographs as a kid and later started selling signed photos. He opened his auction house five years ago and last year sold $9 million worth of autographs, historical documents and movie memorabilia, up from $5 million in 2011.

“People come to us with their Emmys, Tonys, Academy Awards – that’s really what we’re known for,” Sanders said. “Now that we’re big in movie memorabilia, when people have great items, they call me.”

Sanders, a self-trained expert in celebrity signatures, bought the Richard III note at an auction and hopes to sell it for upwards of $75,000. The Fitzgerald poems – one of which references Zelda Fitzgerald’s mental illness – are being auctioned along with other items from the estate of actress Helen Hayes, who knew Fitzgerald.

Sanders expects the poems, which will be sold alongside a signed first-edition copy of Fitzgerald’s novel “Tender Is the Night,” to fetch at least $50,000.

– James Rufus Koren