[Kurt S]

Quoting from a recent post on the NCRS Tech Board:

"After 1968, tires were required to have DOT source code info molded into the sidewall. For the first several years, the code/sequence was manufacturer-proprietary, but starting in 1971, the sequence was standardized into a 10-digit code with the last three digits representing the month/year of manufacture. When the century rolled over, the sequence was extended to eleven digits, with the last four indicating month/year".