Head harness from ca. 1900. (Pro Football Hall of Fame)

Flat top style helmet from ca. 1910. (Pro Football Hall of Fame)

Zuppke style helmet from ca. 1925, the Zuppke helmet was designed by University of Illinois coach Bob Zuppke and was the first helmet to feature full head protection. Its head harness and sponge rubber crown helped prevent concussions. (Pro Football Hall of Fame)

Dayton Triangles helmet from 1928, the Triangles were Charter members of the NFL in 1920. (Pro Football Hall of Fame)

Chicago Bears helmet from 1934 worn by Pro Football Hall of Fame member George Musso. This helmet features fibre shell technology used from the 1930s to the early 1950s. (Pro Football Hall of Fame)

Detroit Lions plastic helmet worn by Pro Football Hall of Fame member Jack Christiansen in the early 1950. This helmet is an early version of the plastic helmet which was invented in 1939 but due to plastic shortages was not in use in the NFL until after World War II. (Pro Football Hall of Fame)

Chicago Bears helmet worn by Pro Football Hall of Fame member Bill George in the 1960s. (Pro Football Hall of Fame)

Pittsburgh Steeler and Pro Football Hall of Fame member �Mean� Joe Greene�s helmet from the 1970's. (Pro Football Hall of Fame)

The modern helmet worn by Bruce Smith of the Buffalo Bills in 1990. (Pro Football Hall of Fame)

A Detroit Lions helmet from 2012. (AP Photo/Scott A. Miller)