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Otero 251

 

Otero 251Otero 251

Description

Form movements are nothing spectacular. Form movement with date indication are already pretty rare, and when you restrict it to ladies' size, there's not much to find.

One of the rare ladies' watches form movements with date indication is the Otero 251, which bases on the Otero 25 and adds a simple calendar mechanism on top. With its nominal size of 5 1/4 lignes (17.4 x 19.9mm) it is a really tiny movement.

base platebase plate

You see on the base plate, that all bearings, except those of the minute wheel, are equipped with rubies. You also see the stocky multi-storey construction, on which the bearing of the fourth wheel are above the escapement wheel.

gear traingear train

The gear train consists of a large directly driven center minute wheel, followed by two tiny wheels, the third and fourth wheel, and finally the escapement wheel. It's hardly possible to construct an even smaller gear train.

side view of the gear trainside view of the gear train

On the side view, the tiny gear train is even more impressive.

The Otero 251 has got a screw balance, which is beared in two Monorex shock protections. It beats contemporarily slow with 18000 A/h and can be adjusted by a long regulator arm. The escapement is a conventional swiss pallet lever escapement.

empty dial sideempty dial side

Without calendar module, the dial side is almost identical to that of the Otero 25, the only difference are two sleeves at the outer edges at 11:30 and 5:30 o'clock which fix the calendar module (which is mounted with two screws at 6:30 and 1:30 o'clock) and the double hour wheel, which drives the calendar mechanism.

The Otero 251 has got a rocking bar winding system and a ratchet on the dial side, which is very well made with a true ratchet.

dial side with calendar moduledial side with calendar module 

The construction of the date indication is pretty simple: The hour wheel drives the switching wheel at 12 o'clock which rotates once a day and which has got a finger on its inner side, which advances the date disc. The spring at 9 o'clock ensures, that the date wheel locks properly. By turning the time backwards and fourth between 9 pm and 1am, the date can be corrected semi-fast.

The calendar module is mounted onto the dial side of the movement with the two well visuable screws.

Otero 251: Dial sideOtero 251: Dial side

Since the date is pretty small, there's a tiny loupe in the crystal.

 

  

 

 Technical data

ManufacturerOtero
Caliber251
Number of jewels17
EscapementAnchor with pallets
BalanceNickel screw balance
Shock protection(s)Monorex
Balance cock directionclockwise
Hairspring studfixed
Regulator typeLong regulator arm
Movement constructionFork
Escapement wheel, Fourth wheel, Third wheel, Center wheel, Mainspring barrel
Construction typesolid construction
Winding mechanismRocking bar
Setting lever spring1 holes
FeaturesQG,RDR
FunctionsHour, minute, day
Beats per hour18000
Size51/4''' (measured: 17,4 x 19,9 mm)
Image in Flume Werksucher 1962 29
Inventory ID 17034
Otero 251OteroOtero2515 1/4'''Otero 25117 Jewels, 5 1/4''', 18000 A/h, QG,RDR
Factsheet

 

 

Usage gallery

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