Notorious B.I.G. and Tupac Shakur are being united for an auction at Sotheby's, the first-ever dedicated hip-hop auction at a major international auction house.

Onetime friends who became rivals in a hype-fuelled war between the East and West Coast rap scenes, Shakur and the Notorious B.I.G. — also known as Biggie Smalls — were gunned down within months of each other. Both crimes remain unsolved.

The estimates for the headlining lots — US$ 200,000 - US$ 300,000 for the crown and US$ 60,000 to US$ 80,000 for the letters — are low, with the hope the auction house can attract first-time bidders and show it is not just a stuffy place for multi-million-dollar watches and paintings.

Bidders will be able to vie for the crown worn (pictured) and signed by the Notorious B.I.G.

Notorious B.I.G. wore the crown during a 1997 photo shoot, three days before he was killed in Los Angeles.

They'll also get to bid on an archive of autographed love letters.

Shakur's letters — many on lined stationary pages with neat hand-lettered script — were written in 1987 and 1988 to Kathy Loy, a fellow student at the Baltimore School for the Arts.

The 42 pages chronicle their approximately two-month long romance, including a letter of regret for breaking up sent a year later.

Loy provided the letters for auction.

"The impact of hip-hop is everywhere — sneakers, clothing, jewellery, art, music. I wanted to have a sale that really recognized how massive that impact really is," said Cassandra Hatton, the Sotheby's senior specialist who organised the sale.

"I've seen the crown. Everybody's seen the crown. It's so famous. It's so iconic. When I was first thinking of doing this sale, I thought, 'Wouldn't it be great to track that crown down?'

"I've sold all sorts of wild things. But this is a little different."

The auction continues Sotheby's recent trend toward embracing items prized by popular culture, including hosting the first dedicated sneaker auction at one of the big auction houses in July 2019.

A pair of Michael Jordan's (pictured) signed, game-worn Nikes was recently auctioned by Christie's for a record $615,000.