A watch spec sheet looks neutral. But every line on it was chosen, and so was every line left off. Learning to read one is mostly learning which numbers matter, which ones are flattering, and what it means when a maker stays quiet.
The examples below come from watches we cover, with figures checked against the makers.
Caliber
The caliber is the name of the movement, and it is the most useful line on the sheet because it lets you compare watches that look nothing alike. Orient’s Kamasu, Mako-3 and AA02 Diver all use the F6922, so their timekeeping specs are the same whatever the dial. All three are available at Orient Watch USA. Seiko’s 4R36 runs both the $350 SRPD and the $450 SRPL83.
A named caliber also tells you where it came from. Hamilton’s H-10 is based on the Powermatic 80 that Tissot uses, and both brands belong to the Swatch Group. The Sellita SW200-1 in the Christopher Ward C60 Trident comes from an outside supplier.
When a maker does not name the movement, that is worth noticing, and it pays to read past the sales copy. Timex’s description of the Marlin Automatic calls the movement only a 21-jewel automatic, while its specification table names the Miyota 8215.
Jewels
Jewels are synthetic ruby or sapphire bearings placed where parts turn against each other, to reduce friction and wear. Wikipedia notes that a fully jeweled time-only watch typically has 17.
So a higher count is not a quality score. Hamilton’s hand-wound H-50 has 17 jewels and runs for 80 hours. Seiko’s 4R36 has 24 and runs for about 41. Treat the jewel count as a description of the movement’s layout, not a ranking.
Beat rate
Beat rate, given in vibrations per hour (vph), is how often the balance swings. Most watches in this market run at 21,600 vph, or 3 Hz, which works out to six steps of the seconds hand per second. That includes Orient’s F6 calibers, Seiko’s 4R, Citizen’s 8204 and 8210, Tissot’s Powermatic 80 and Hamilton’s H-10 and H-50.
The SW200-1 runs at 28,800 vph, or 4 Hz, so its seconds hand takes eight smaller steps a second and looks smoother. Faster is not automatically better. The 4 Hz Sellita has a 38-hour reserve, while the 3 Hz Powermatic 80 has 80.
Power reserve
Power reserve is how long a fully wound watch runs before it stops. It decides whether you can take the watch off for a weekend and still find it running.
Most figures in this price range fall into two groups. Orient’s F6 calibers give about 40 hours, Seiko’s 4R about 41 and Citizen’s 82 family about 42. Tissot’s Powermatic 80 and Hamilton’s H-10 and H-50 give 80. Seiko’s 6R55 in the Alpinist sits in between at about 72.
Rated accuracy
This is the number most buyers skip and the one that tells you most about a maker’s confidence. It is a tolerance in seconds per day that the maker is prepared to publish.
Orient rates the F6922 and F6724 at +25/−15. Seiko rates the 4R35 and 4R36 at +45/−35. Citizen rates its 82 family at −20/+40. Christopher Ward rates the C60 Trident at +12/−5, and Orient Star’s newer calibers are rated at +15/−5.
For comparison, COSC, the Swiss chronometer testing body, certifies a mechanical movement only if it averages −4/+6 seconds a day. Each uncased movement is tested for 15 days, in five positions and at three temperatures. The Longines Spirit Pilot is COSC certified. Grand Seiko rates the 9S64 in its new SBGW325 at +5/−3 seconds a day static, a figure measured off the wrist.
Some makers publish no rating. Hamilton gives none for the H-10 in the Khaki Navy Scuba. That does not make the watch inaccurate, but it asks you to take its timekeeping on trust.
Hacking and hand-winding
Hacking means the seconds hand stops when you pull the crown out to set the time, so you can set it to the second. Hand-winding means you can wind the mainspring with the crown rather than relying on wrist movement.
Neither is guaranteed at this price. Orient’s older 46943 and 48743 calibers had neither, and Monochrome’s 2018 review of the Timex Marlin Automatic reported a Miyota 8215 that did not hack. Today’s F6922, F6724, 4R36 and Citizen 8204 do both. A hand-wound watch like Hamilton’s Khaki Field Mechanical has no rotor at all, so you wind it by hand regularly.
Crystals
The crystal is the clear cover over the dial, and it is an easy place for a maker to save money without saying so.
- Acrylic. A plastic, light and highly impact resistant, which is why Wikipedia notes its long use in dive and military watches. It scratches more easily than glass. The Timex Marlin uses a domed acrylic crystal.
- Mineral. Tempered glass. The Bambino and the AA02 Diver use it. Harder than acrylic, softer than sapphire.
- Hardlex. Seiko’s own name for the mineral glass it fits to many of its watches. Like other mineral glass, it is softer than sapphire. The Seiko 5 Sports and the Presage use it.
- Sapphire. Synthetic sapphire, the most scratch-resistant option. It is hard to cut and polish, which makes it the most expensive. The Kamasu, Tsuyosa, Promaster and Khaki Field all have it.
Two details are worth checking. One is anti-reflective coating, which cuts glare. Hamilton lists it on the Khaki Navy Scuba and Christopher Ward on the C60. The other is the caseback. Citizen’s Tsuyosa has a sapphire front crystal but a mineral glass display back.
Water resistance and ISO 6425
A water resistance rating is not a depth. Under ISO 2281, the standard for everyday watches, it is a pressure that a sample of new watches was tested to, once, under static conditions. The usual guidance, as Wikipedia summarizes it, is that 30m means splash resistant, 50m covers shallow swimming, 100m covers swimming and snorkeling, and 200m covers skin diving.
ISO 6425 is the separate standard for diver’s watches. It requires at least 100m, testing at 125 percent of the rated pressure, a timing device such as a unidirectional bezel, legibility at 25cm in the dark and a running indicator such as a luminous seconds tip, along with magnetic, shock and saltwater tests. A compliant watch can be marked “DIVER’S” with its depth.
Here the wording matters. Seiko’s SRPL83 has a unidirectional bezel and 100m but no ISO 6425 rating. Hamilton’s Khaki Navy Scuba is also 100m and not ISO rated. The Kamasu is 200m, and Orient makes no ISO claim for it. Citizen describes the Promaster Dive Automatic as ISO compliant at 200m, and the Orient Star Sports Diver is ISO 6425 rated. If you will actually dive, that last distinction is the one to look for.
A water resistance rating is a test pressure, not a depth. The word that matters to a diver is ISO 6425.
Lug width, lug-to-lug and thickness
Diameter gets the attention, but three other numbers decide how a watch fits.
Lug width is the gap the strap fits into, and it decides which straps you can buy. Most watches here use 20mm or 22mm. The Bambino 40.5 is an exception at 21mm.
Lug-to-lug is the distance from the tip of the top lugs to the tip of the bottom ones, and it decides whether a watch overhangs your wrist. Hamilton’s Khaki Field Mechanical is 38mm across but 47mm lug-to-lug, the same as Orient’s 41.8mm Kamasu. The 38.4mm Bambino is 44mm. We look at this more closely in The Quiet Return of the 38mm Watch.
Thickness decides whether the watch slips under a cuff. The quartz Tissot Everytime 40mm is 7.07mm. The automatic PRX Powermatic 80 is 10.93mm and Seiko’s SRPL83 is 13.9mm.
What is missing
The last skill is reading the gaps. Citizen does not publish thickness or lug-to-lug for the Promaster Dive Automatic. Hamilton does not publish an accuracy rating for the H-10. Neither is a reason to rule a watch out, but each one is a question to answer before you buy.
A good spec sheet lets you compare two watches without seeing either. To try it, read our side-by-side of the Orient Kamasu and Seiko 5 Sports, or apply these tests to a budget in Can a $300 Mechanical Watch Be a Serious Watch?.
