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Ebosa 71
Manual · 16‴ · Switzerland · 1950
Dimensions
36.8 mm
Height
4.70mm
Jewels
15
Power reserve
30h
Timegrapher
Beat rate
17,280bph
Frequency
2.4Hz
Reference: healthy amplitude ≈ 270–315° fully wound (>200° at 24 h); beat error ideally < 0.5 ms.
Movement
| Movement type |
Manual
Purely mechanical movements wound by hand via the crown, which tensions the mainspring to store energy. As the spring unwinds, it drives the gear train at a controlled rate set by the escapement and balance. Typical power reserves range from 38 to 80 hours, requiring daily or near-daily winding to keep the watch running.
|
|---|---|
| Winding type |
Stem Winding (Crown)
Winding the mainspring by turning the crown attached to the stem, transmitting torque through the winding pinion. Patented by Adrien Philippe in 1842, it replaced key winding and remains the standard manual winding method for both pocket watches and wristwatches.
|
| Setting type |
Pin Set (Pin-Push)
A small pin or button next to the crown is depressed to engage the setting mechanism while the crown is turned. A transitional system between key set and modern stem set, common in pocket watches from the 1860s to early 20th century and in some lower-cost wristwatches.
|
| Escapement type |
Pin Lever
Also known as the Roskopf escapement, this is a simplified, low-cost variant of the Swiss Lever using steel pins instead of jewelled pallet stones. Less accurate but inexpensive to produce, it democratized mechanical watchmaking in the 20th century, populating affordable alarm clocks and entry-level watches worldwide.
|
| Control type |
Balance Wheel
The heart of mechanical timepieces, the balance wheel is an oscillating component that, together with the hairspring, forms a harmonic oscillator regulating the gear train's pace. Its steady back-and-forth motion ensures the even release of energy from the mainspring, governing the watch's accuracy.
|
| Regulator type |
Pinned Regulator (or Index Regulator)
The most traditional regulator, consisting of a movable index pointer fitted with two curb pins (or a pin and a boot) that embrace the hairspring. Sliding the index along its scale changes the spring's active length, adjusting the rate. Simple, reliable, and easy to service, it remains the workhorse standard across countless mechanical movements.
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Specifications
| Lignes | 16‴ |
|---|---|
| Shape |
Round
It is the most common form that we can find.
|
| Complications |
Sub Second
A small seconds hand typically located on a sub-dial and is separate from the central hour and minute hands. Originating from early pocket watches where the main balance wheel drove the seconds hand, it offers an elegant way to track the passage of time without crowding the main display. It remains a testimony to the watch's mechanical precision and history.
|
| Hand count | 3 |
| Hand sizes | 2.10 x 1.20 / 0.25mm |
| Further measures | Mounting Diameter (Dm): 36.1mm Winding Gear: 0.5mm Stem height (T): 2.5mm Mounting Height (F): 0.6mm |
Origin & References
| Manufacturer | Ebosa |
|---|---|
| Country | Switzerland |
| Launch year | 1950 |
| COSC certified | No |
| Signature | ca. 1950: - Ebosa 71 |
Notes
Remarks: open face calibre
pin-lever escapement
nearly perfect imitation of balance screws
indirect minute, hand friction clutch on barrel (Roskopf type)
Other data: balance staff: U1878 stem: W1447 stem ronda: 976 (16) Mainspring: 1.500 x 17.500 x 0.190 x 780.000 mm
pin-lever escapement
nearly perfect imitation of balance screws
indirect minute, hand friction clutch on barrel (Roskopf type)
Other data: balance staff: U1878 stem: W1447 stem ronda: 976 (16) Mainspring: 1.500 x 17.500 x 0.190 x 780.000 mm
Compatible Parts
3 other catalog sources can supply compatible parts for this caliber.
3 compatible parts catalogued · find a donor to harvest a scarce part.
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