Steel third worm gear used in 1953-1977 Speedometers and 1953-1958 Tachometers with rev counter.
GM serviced this part for many years in plastic. Steel is required to ensure longevity. Note: This is not a cure-all for an odometer that has become inoperative! It is a replacement for one of the 3 gears in the gear train that drives the odometers.