Seiko 2101

 
Seiko 2101

Seiko 2101

Description

The Seiko 2101 is most probably their very first selfwinding movement for ladies’ watches, made in the early 1960ies. Since it there’s no caliber number marked on it, the identification was pretty difficult.

base plate

base plate

The base plate shows no signs of a selfwinding movement. It’s the base plate of a regular form movement with a size of 6 3/4 x 8 lignes, well executed with all important bearings containing rubies.

gear train

gear train

The gear train is standard for this kind of movement: The mainspring barrel drives the center minute wheel, followed by the almost identically sized third and fouth wheel, and finally there’s the steel escape wheel. This wheel is beared in a chaton on the gear train bridge.

side view of the gear train

side view of the gear train

The two-leg Glucydur anular balance beats with 19800 A/h and is beared in two Seiko inhouse Diashock bearings. The beating frequency can be adjusted with a long regulator arm.

movement w/o selfwinding module

movement w/o selfwinding module

On the right, next to the ratchet wheel, you can see the space, into which the only one-side beared driving wheel from the selfwinding module is put into.

selfwinding gear train

selfwinding gear train

The complete selfwinding mechanism consists of only four gears, the driving wheel, a further reduction wheel (also beared singled-sided) and two pawl exchange wheels, whose upper sides engage with the oscillating weight.

selfwinding module, lower side

selfwinding module, lower side

The selfwinding module is attatched to the base movement with three screws.

There’s no early decoupling when the movement is wound manually, the oscillating weight is detached only by the two exchange wheels.

movement without oscillating weight

movement without oscillating weight

The pretty filigree oscillating weight is axle-beared and secured with a screwed plate.

oscillating weight

oscillating weight

On the dial side, there are no indications, that we have a selfwinding movement here.

Seiko 2101: Dial side

Seiko 2101: Dial side

This early selfwinding movement is not only interesting by its shape and size, another interesting detail is, that it is one of the very few selfwinding movement, which only display hours and seconds and don’t offer a seconds or a date indication.

In the lab

Probably taken out of a melted golden ladies’ watch, only the movement, dial and case back survived and came into the lab.

Timegrapher result

This movement got a light revision. The results on the timegrapher, it showed afterwards, are more than impressive, not only in absolute figures, but most of all for such a small movement. And the beat error is perfect, especially, when you take into account, that the hairspring is connected to a fixed stud and the beat error is very hard to correct.

horizontal positions
dial up +3 s/d 225° 0.0ms
dial down +16 s/d 232° 0.0ms
vertical positions
crown right (12 up) +15 s/d 210° 0.3ms
crown up (3 up) +23 s/d 216° 0.0ms
crown left (6 up) +13 s/d 216° 0.2ms
crown down (9 up) 0 s/d 215° 0.1ms

Technical data

Manufacturer:Seiko
Caliber:2101
Size:6 3/4 x 8''' (measured: 15,5 x 17,9mm)
A/h:19800
Number of jewels:21
Escapement:Pallet lever
Balance types: Glucydur anular balance (two legs)
Shock protection(s): Diashock (Seiko)
Balance bearing / direction hairspring:Counterclockwise
Moveable stud:no
Adjust mechanism:Long regulator arm
Construction:
  • lever
  • escape wheel, seconds wheel, third wheel, center minute wheel
  • mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Setting lever spring:4 hole(s)
Features:
  • AUT (selfwinding)
Production period:1963 - 19??
Inventory number:20041

Usage gallery

Seikomatic Lady ladies' watch  (case missing)

Seikomatic Lady ladies' watch (case missing)