Seiko 3100
At the end of 1968 or the beginning of 1969 Seiko marketed its first electric watch, the 'Electronic 31A', without date, frequency 6 Hz. It was followed in May 1969 by the Seiko 3102A, with date and corrector. Production quantity: 13.400 pieces.
Seiko 3200
1972. Caliber 3202A. Frequency 6 Hz.
Seiko 3300
1972. Seiko released its 3300 series, caliber 3302 and 3303, also known under the name 'Seiko Tradition'. A peculiar watch, equipped with both mechanical contacts and a transistor. The frequency is 3 Hz. The electrical current through the contacts is very small and only needs to steer a transistor. The transistor switches the much larger current to magnetise the coils and give the balance wheel an impulse.
Seiko 3700
EL-370 or 37 A. Frequency 6 Hz.
Seiko 3702 A with date and Seiko 3703 B with day and date were launched in April 1971.
Seiko 07 series, Elnix
1973. Caliber 0723A, 0703A and 0702A. Frequency 4 Hz.