The most coveted option, sport seats were manufactured by Recaro and introduced in 1967. There are 4 types of sport seats.
The 1967 MODEL had no headrest provision, an attachable headrest was available as an option.
The 1968 MODEL was identical to the 1967 model except a headrest was incorporated as standard equipment.
The 1969 MODEL was slightly different than the 1968 model and was used through 1971.
The 1972 MODEL was slightly different than the 1969 model, it incorporated inertia reel retractable seat belts and was used through 1973. In 1973 a double locker system replaced the single locker system for increased safety.
The 1973 911 window sticker shows that sport seats were a mere $99.00 option. Inexpensive as that seems today, few 911s were ordered with sport seats making them rare and very valuable.
Reproduction sport seats are available from several manufacturers and are a reasonably priced alternative to originals.