Front view
Dial, hands and bezel as delivered.
Case-back view
Case-back engraving and, where fitted, the sapphire display.
Movement
Calibre with its finishing and decoration.
On the wrist
Worn shot for proportion and strap drape.
Sinn · Hydro
Sinn Hydro 38 mm Slate 18k
Reference 87144OR.61
Reference at a glance
- Brand
- Sinn
- Collection
- Hydro
- Model
- Sinn Hydro 38 mm Slate 18k
- Reference number
- 87144OR.61
- Year / era
- 1985 · 1980s — mechanical revival
- Complication
- Perpetual calendar
- Movement
- Automatic, 38-hour reserve
- Case material
- 18k yellow gold
- Dial type
- Slate grey
- Strap / bracelet
- Milanese mesh
- Water resistance
- 50 m
- Limited-edition status
- Regular production, not a limited edition
Case, dial & bracelet
- Case dimensions
- 38 mm
- Case thickness
- 12.6 mm
- Case material
- 18k yellow gold
- Bezel
- Octagonal with 8 hexagonal screws
- Crystal
- Flat sapphire with Cyclops lens
- Dial
- Slate grey
- Hands
- Rhodium-plated baton hands with luminous fill
- Indexes
- Applied Roman numerals
- Bracelet / strap
- Milanese mesh
- Clasp / buckle
- Triple-folding clasp with safety catch
- Water resistance
- 50 m
Movement
- Movement / calibre
- Calibre 51F — Automatic, 38-hour reserve
- Movement type
- Manual-winding
- Frequency
- 21,600 vph (3 Hz)
- Power reserve
- 5 days
- Number of jewels
- 40 jewels
- Complications
- Perpetual calendar
- Functions
- Chronograph, tachymeter, date
- Watchmaker
- Assembled and regulated by a single watchmaker, who signs off the piece before casing.
Production & market
- Production period
- 1985 – 1997
- Limited-edition quantity
- Not applicable
- Current market information
- Thin secondary-market supply — pricing is set piece by piece at auction.
Designer
Gérald Genta
Gérald Genta (1931–2011) trained as a goldsmith in Geneva and became the most influential watch designer of the 20th century. Working freelance, he sketched the Audemars Piguet Royal Oak overnight in 1970, followed by the Patek Philippe Nautilus, the IWC Ingenieur SL and the Bulgari Bulgari — defining the integrated-bracelet luxury sports watch as a category.
Historical significance
Sinn Hydro 38 mm Slate 18k sits within Sinn's Hydro line, introduced in 1985. It carries the house codes established since 1961 — 18k yellow gold case, slate grey dial and automatic, 38-hour reserve — and is one of the references collectors use to date the evolution of the collection.
Interesting facts
- The bracelet tapers across its length, which is why the profile looks thinner on the wrist than the specification suggests.
- The reference was originally planned as a one-year run and stayed in the catalogue for well over a decade.
- The case is finished by hand, alternating polished and satin-brushed surfaces in a single pass so the edges stay razor sharp.
The House
Sinn
Brand facts
- Founding year
- 1961
- Founder
- Helmut Sinn
- Headquarters
- Germany
- Tier
- Affordable & Tool Watches
- Major collections
- 556, 104, EZM, U1, 903, Hydro
- Signature technologies
- Anti-magnetic silicon escapement · Shock-absorbing movement mounting
- Famous movements
- Automatic, 38-hour reserve · Automatic Powermatic 80 · Automatic COSC chronometer · Quartz
- Notable watches
- Sinn 556 42 mm Silvered 18k (1975) · Sinn 556 43 mm Slate Sapphire (1961) · Sinn 556 36 mm Mother-of-pearl 18k (1976) · Sinn 556 43 mm Ice 18k (1965)
Brand history
Sinn has spent more than 65 years refining a single idea: a watch should outlive its owner. From the earliest workshop pieces to today's 556, the house has balanced technical ambition with a recognisable design language, and its collections remain among the most closely followed by collectors worldwide.
Helmut Sinn established Sinn in 1961, working from Germany at a time when precision was measured by hand. The founder's obsession with finishing and accuracy still defines every Sinn calibre produced today.
Historical milestones
1961
Helmut Sinn founds Sinn in Germany.
1969
The quartz era forces Sinn to redefine mechanical watchmaking.
1990
Sinn enters the modern collector market with its signature lines.
2024
Sinn continues to produce 556, 104, EZM and other icons in limited numbers.