Flown external shingle from the Mercury-Atlas 8 Sigma 7 spacecraft that carried astronaut Wally Schirra around the Earth six times on October 3, 1962, famously painted with the mission emblem by Cece Bibby. This historic flight doubled the flight time of prior flights, and Schirra went on to become the only person to fly Mercury, Gemini and Apollo missions.
Schirra’s recollection: “I named my spacecraft Sigma Seven. Sigma Σ, a Greek symbol for the sum of the elements of an equations, stands for engineering excellence. That was my goal – engineering excellence. I would not settle for less. Scientific observations were on my agenda as well. I observed the planet Mercury, not normally seen from earth, because the apparent position of Mercury is close to the sun. In orbit we’re not affected by the diffuse light of the atmosphere, so I would see Mercury as it passed through layers of light. I tracked its passage against a yardstick of time.”
The mission objectives involved evaluating the performance of the spacecraft over six orbits, as well as the effect of prolonged microgravity on the pilot. The specific spacecraft systems would also be evaluated and tested, and the worldwide tracking and communications network would be tested to see how well it would stand up in an extended mission. The flight control experiments included manually turning the spacecraft around, yaw and pitch manoeuvres to determine how easy it was to control the spacecraft attitude, realignment of the onboard gyroscopes in flight, and leaving the spacecraft to drift on-orbit.
By the fifth orbit, Schirra had begun to relax, commenting that it was the first rest he had had since December 1961.
From the space auction site: this ∑7 shingle measures 20″ x 18″, and features the burnt remnants of Bibby’s painting of the ‘Sigma 7’ emblem in red, white, and yellow, along with the “J37” and “J20” coupler port markings at the bottom.
In order to understand the effects of reentry on the materials used for the shell of the Mercury capsule, NASA transferred this panel to Dr. John F. Radavich of Purdue University for destructive evaluation.
The shingles of the Mercury capsules were composed of a nickel-based high temperature alloy called René 41, used due to its ability to retain high strength at extreme temperatures. In August 1962, he published a paper entitled ‘Microstructural Changes Produced in Orbited Rene’ 41 Heat Shingles,’ in which he noted that the panel surfaces displayed no obvious meteorite impacts; that the outer oxide layer undergoes an enrichment of chromium oxide relative to preflight material; and that the amount of M6C carbide phase in flown material decreases relative to the TiC phase, among other observations.
This shingle is of particular importance, as it boasts the original hand-painted ‘Sigma 7’ insignia by Cece Bibby. In 1959, Bibby was hired by Chrysler Aerospace and soon began work as a contract artist for NASA, her workspace located just across the street from the astronaut office. Not a fan of the stencil designs on the Freedom 7 and Liberty Bell 7, John Glenn recruited Bibby in 1962 to design and paint by hand the emblem for his Friendship 7 spacecraft. In addition to Glenn, Bibby went on to create the designs for Scott Carpenter’s Aurora 7 and Wally Schirra’s Sigma 7 capsules, subsequently becoming the first and only woman to ascend the Mercury launch gantry and go inside the ‘white room’ that surrounded the vehicle.
And a 
Assisted entry by Gordie Cooper, with a nice signed tribute to Cece:
The Mercury-Atlas 8 rocket all shiny and new, before cryogenic-propellant loading:
Blastoff! With Wally Schirra up top
The landing was surprisingly precise, 4.5 miles (7.2 km) from the target point and 0.5 miles (0.80 km) from Kearsarge, and Schirra joked that he was on course for the recovery carrier’s "number three elevator". The capsule hit the water, submerged, and bobbed to the surface again, righting itself after about 30 seconds. Three pararescue swimmers were dropped by one of the helicopters to help him climb out, but Schirra radioed that he would prefer to be towed to the carrier, and a whaleboat from Kearsarge was sent with a line. Forty minutes after landing, Sigma 7 was hoisted aboard Kearsarge; five minutes later, Schirra blew the explosive hatch and climbed out to a waiting crowd. As recovered: 
The back of the panel is marked along the edge in white paint, "45-32 235-129," and marked in black ink, "S/C #16, Shop #10." Also attached to the reverse are segments of the thermocouple probes. The panel has several cuts along the top edge, where material was removed for analysis.
Dr. Radavich’s obituary makes note of his distinguished career as a researcher: ‘His principal contribution to high temperature material technology had been his pioneering work in the transition of analytical procedures from optical to electron microscopy. In so doing, he developed preparation procedures that opened the doors to all future metallographic studies of superalloys. The current state-of-the-art practices for phase extraction and identification are dependent upon the fundamental knowledge that he developed.’
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