Seiko 5100

Seiko's 51 Stream was a family of midrange automatic watch movements from Seiko produced in the late 1960's into the early 1970's. It is notable for the quickset date pusher located inside the crown and this function was the namesake for the Seiko "Presmatic" line. It was produced by Daini Seikosha.

Three 51 Stream movements were introduced in 1967: The 33 jewel 19,800 A/h 5106 found in the domestic "Seikomatic-P", and two "Seiko New Fives", the basic 23-jewel 5126 and the "DX" (deluxe) 5139 with 27 jewels. In 1969, a Hi-Beat (28,800 A/h) "Presmatic" was introduced with a new 5146 movement sporting 27 or 30 jewels, just as the 5139 was phased out. The movement stream began disappearing just one year later, with the 5106 and 5126 ending production in 1970 and the last surviving member, the 5146, gone in 1971.

The 51 Stream is somewhat similar in appearance to the Daini-produced 52 Stream, introduced in 1969 as the ultimate mechanical movement from that company. It is a fairly advanced movement, with hacking seconds, hand winding, a "tadpole"-style fine adjuster, and quickset date (though the day is not quickset). All 33 jewels are functional, with 6 being cap jewels and jewels on both sides of the barrel arbor. It lacks the bilingual day wheel of other contemporary Seiko movements.

Variants

Movement	Date	Winding	Speed	Hands	Date	Jewels
5106A	1967-1970	Automatic	19,800 A/h	Hour, minute, seconds	Day and Date	33
5126A	1967-1970					23
5139A	1967-1969					27
5146A	1969-1971		28,800 A/h			27 or 30

External links

• Seiko - 51 Presmatic & Seikomatic-P family

Description: Automatic movement Functions: Hours, minutes, seconds Automatic winding Quickset date wheel Hacking Hand winding Day wheel Data: 23, 27, 30, or 33 jewels 19,800 or 28,800 A/h Production period: 1967-1971