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Unitas 285
Manual · 16.5‴ · Switzerland · 1940
Dimensions
37.2 mm
Height
4.20mm
Jewels
15
Power reserve
40h
Timegrapher
Beat rate
18,000bph
Frequency
2.5Hz
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 |
Stem Set (Crown Pull)
The dominant modern system: pulling the crown out to a setting position engages the hand-setting mechanism. Introduced in the late 19th century and refined into multi-position crowns (date, time, GMT). Used in virtually all modern wristwatches and most 20th-century pocket watches.
|
| Escapement type |
Swiss Lever
The undisputed standard of modern mechanical watchmaking. Through an elegant interplay between escape wheel, pallet fork, and balance, it delivers reliable impulses with the safety of 'draw' to keep the lever locked. Refined since the 18th century, it powers almost every quality mechanical wristwatch made today.
|
| 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.
|
Specifications
| Lignes | 16.5‴ |
|---|---|
| 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 | 2.00 x 1.15 / 0.27mm |
| Further measures | Mounting Diameter (Dm): 36.6mm Stem height (T): 1.85mm Mounting Height (F): 0.5mm |
Origin & References
| Manufacturer | Unitas |
|---|---|
| Country | Switzerland |
| Launch year | 1940 |
| In-house | No |
| COSC certified | No |
| Signature | ca. 1940: 490, Swiss Made, 15 Jewels - Unitas
(Unitas 490, 17.5" ) |
Notes
Remarks: open face calibre
varying bridge shapes
attention: probably left handed ratchet-wheel screw (cf. Unitas 490)
differences not known between 285, 293, 299, 303, 327, 331, 335, 339, 345, 497
Other data: balance staff: U991 stem: W1418 mainspring / battery: Zf3016, 1.50 x 15.0 x 0.18 x 450mm balance staff ronda: 2382 (16,5-17,75) stem ronda: 1138 (18,5-21)
varying bridge shapes
attention: probably left handed ratchet-wheel screw (cf. Unitas 490)
differences not known between 285, 293, 299, 303, 327, 331, 335, 339, 345, 497
Other data: balance staff: U991 stem: W1418 mainspring / battery: Zf3016, 1.50 x 15.0 x 0.18 x 450mm balance staff ronda: 2382 (16,5-17,75) stem ronda: 1138 (18,5-21)
Family
Series 226 - 501
226: sweep second, H= 5.2mm
283: open face, H= 4.9mm
285: open face, H= 4.2mm
286: hunter, H= 4.2mm
287: open face, H= 3.7mm
343: open face, H= 6.05mm
490: open face, H= 4.2mm, only 17.5"
501: open face, H= 5.0mm, date
283: open face, H= 4.9mm
285: open face, H= 4.2mm
286: hunter, H= 4.2mm
287: open face, H= 3.7mm
343: open face, H= 6.05mm
490: open face, H= 4.2mm, only 17.5"
501: open face, H= 5.0mm, date
Related calibers
Unitas 226
Unitas 283
Unitas 285
Unitas 286
Unitas 287
Unitas 289
Unitas 291
Unitas 293
Unitas 295
Unitas 297
Unitas 299
Unitas 303
Unitas 307
Unitas 309
Unitas 327
Unitas 329
Unitas 331
Unitas 333
Unitas 335
Unitas 337
Unitas 339
Unitas 341
Unitas 343
Unitas 345
Unitas 348
Unitas 349
Unitas 351
Unitas 353
Unitas 355
Unitas 490
Unitas 493
Unitas 497
Unitas 498
Unitas 499
Unitas 501
Compatible Parts
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