Marilyn wore faux pearl earrings and slipped on a faux pearl necklace for the photo spread -- famously known as the "Last Sitting" -- with legendary fashion photog Bert Stern.

The pics were snapped just 6 weeks before her death, and they're going up for sale through online auction house Gotta Have Rock and Roll, where they're expected to fetch a pretty penny.

The jewelry is cool, but so is the Nikon camera Bert used to take thousands of photos that day, and it's also up for auction. While Vogue Magazine supplied the props, clothes, jewelry and accessories ... the camera was Bert's personal one.

Marilyn even used the camera as a prop, spontaneously grabbing the Nikon while Bert grabbed a spare camera and kept snapping away. The auction house expects the Nikon to fetch $60,000 due to its place in pop culture.

The pearls are expected to bring in $50,000 for the earrings and $8k for the necklace.

Some of Marilyn's extensive wardrobe is also part of the auction ... we're told a gown and shawl is estimated to go for $40k and a pair of black and white checkered pants could fetch $15k. MM owned and wore the clothing.

The auction opens July 22 ... good luck!!!