The external skin of the Mercury spacecraft, except for the heatshield, was made of two types of metal shingles. The conical part of the spacecraft was covered with panels like this one of a very specialized nickel steel alloy called Rene 41. These could withstand the high heat of reentry due to their high melting point and ability to radiate away much of their heat. The conical nose of the spacecraft had even more exotic and heat resistant beryllium shingles.

This is from Wally Schirra’s Sigma 7 spacecraft, used on United States third manned orbital mission. The “Sigma” is a Greek character used in maths to denote a summation. Schirra chose it because his mission represented a summation of all the previous ones.

The emblem was painted by artist Cece Bibbi. Notice how, in spite of the heat of re-entry, some of the paint managed to survive.