ETA (Unitas) · ETA 6497 / 6498

Panerai Luminor, Stowa Marine and Hamilton Khaki Field Officer power reserve: inside the ETA 6497 and 6498

Early Panerai Luminors like the PAM 111, the Stowa Marine Original, the Hamilton Khaki Field Officer Handwinding and the Tissot T-Complication Squelette all run on the hand-wound Unitas 6497 or 6498. A full wind lasts about 46 hours, just under two days.

Updated September 2026 · Based on manufacturer specs, published reviews and watchmaker/owner reports

Watches that use the ETA 6497 / 6498

The Unitas 6497 and 6498 are 1950s pocket-watch movements that found a second life in big wristwatches. The two are the same movement laid out differently. On the 6497 ("Lépine"), the small seconds sit opposite the crown, at 9 o'clock. On the 6498 ("Savonnette"), they sit at 6. If your hand-wound watch is 42 mm or more and has a small seconds dial in one of those places, there's a good chance one of these is inside.

Specs at a glance

History and where it came from

Unitas was a movement maker in Tramelan, Switzerland, founded in 1918 and folded into Ebauches SA, ETA's predecessor group, in 1932. The 6497 and 6498 arrived in the 1950s as pocket-watch movements, and Monochrome's history notes that they stayed in production and on sale to outside brands until recently.

Their wristwatch career began with Panerai. When the brand relaunched in the 1990s, it built its Luminor and Radiomir models around the 6497, eventually with its own OP calibres such as the OP XI. The pocket-watch size forced cases of 44 mm and up, and Panerai's success helped make big watches fashionable. Other brands followed with pilot's watches, marine chronometer styles and skeletons, since the large, flat bridges are easy to decorate or cut away.

The -2 versions brought a longer mainspring, Incabloc shock protection, an Etachron regulator and, in some cases, a faster 3 Hz beat. Panerai has since moved to in-house movements such as the P.9010, and Sellita has not made a direct copy, so today's cheaper alternative is the Chinese Seagull ST36.

Accuracy in the real world

The 6497 is simple and responds well to regulation. Many versions, like the Stowa Marine Original, have a swan-neck fine adjuster that lets a watchmaker set the rate precisely. Panerai's OP XI was COSC-certified to -4/+6 s/day, and Monochrome mentions a British maker regulating a modified 6498 to ±3 s/day.

The slow 18,000 vph beat of the -1 is a little less stable than a 4 Hz automatic when the watch is knocked, and the rate tends to change as the spring runs down. Because you wind it daily, though, a hand-wound 6497 spends most of its time on a well-filled spring, which helps.

Reliability and servicing

This is one of the easiest movements in the world to service. It's the most widely used teaching calibre in watchmaking schools, the parts are large, and there's very little to go wrong with no automatic winding or date.

• Independents. Almost any watchmaker will service a 6497 or 6498. Brand-modified versions such as Panerai's OP calibres or Omega's 2201 may need brand parts for the modified components.
• Parts supply. ETA has restricted supply to outside brands, so new movements may get harder to find. For now, parts are plentiful.
• Interval. About five years is the usual guide. If the crown or stem starts to feel rough when winding, mention it at service.

Quirks worth knowing

• No hacking. Standard 6497s and 6498s don't stop the seconds hand when you pull the crown, so setting to the exact second takes a trick: set the minute hand slightly ahead and push the crown in at the right moment.
• Stop at the stop. A hand-wound movement has a firm end to its winding. When the crown stops turning, stop. Forcing it can damage the mainspring.
• Reserve figures vary. The -1 versions run about 46 hours, the -2 versions about 53, and Panerai quotes 56 for the OP XI. We use the 46-hour figure, which matches the Stowa Marine and Tissot Squelette.
• Big cases. At 36.6 mm, the movement sets a minimum case size of about 40 to 41 mm.

How it compares

• Hamilton H-50: Hamilton's modern hand-wound in the Khaki Field Mechanical. Smaller, with an 80-hour reserve.
• Seagull ST2130: Seagull's automatic 2824 clone. Seagull also makes the ST36, a low-cost 6497 copy.
• Vostok 2416B: another rugged, simple movement, but automatic and with only 31 hours.
• Panerai P.9010: the in-house automatic that replaced the 6497 in many Panerais, with 72 hours.
• ETA 2824-2: the automatic alternative with a date and hacking, in a much smaller movement.

Living with the 46-hour reserve

A hand-wound watch doesn't recharge on the wrist, so the reserve counts from the last time you wound it. Wind your Panerai or Stowa Marine every morning and it never stops. Skip a morning and it's still running that evening, but forget on Saturday and Sunday and it will have stopped by Sunday morning.

The trap is rotation. Take a Hamilton Khaki Field Officer off after work on Friday and wear something else all weekend, and it stops around 4pm on Sunday whether it's on a winder or not, since a winder can't wind a hand-wound watch. Watch Winder counts down the 46-hour reserve for each watch you own and reminds you before it stops. To check a particular weekend, try the "Will my watch stop?" calculator.

Verdict

The ETA 6497 and 6498 are simple, tough, easy to service and lovely to look at through a display back. They made the Panerai Luminor what it is and still give watches like the Stowa Marine Original a real pocket-watch feel. The trade-offs are size, no hacking and a daily winding habit. If you enjoy that morning ritual, it's one of the most satisfying movements you can own.

FAQ

How long does a Panerai PAM 111 run when fully wound?

Panerai quotes 56 hours for the OP XI calibre in the PAM 111, a modified ETA 6497-2. Standard 6497-1 movements run about 46 hours.

How often should I wind a Stowa Marine Original?

Once a day, ideally at the same time each morning, until you feel the crown stop. Its Unitas 6498-1 runs about 46 hours from a full wind.

Does the Hamilton Khaki Field Officer Handwinding hack?

No. Its ETA 6497 doesn't stop the seconds hand when you pull the crown, so set the minute hand slightly ahead and push the crown in at the right moment.

Can I use a watch winder for a Panerai Luminor with a 6497?

No. The 6497 is hand-wound and has no rotor, so a winder does nothing. Wind it by the crown instead.

What movement is in the Tissot T-Complication Squelette?

A partly skeletonised ETA 6497-1, hand-wound, with 17 jewels and about 46 hours of reserve.

What is the difference between the ETA 6497 and 6498?

They are the same movement with the small seconds in different places: at 9 o'clock on the 6497 and at 6 o'clock on the 6498.

Can I overwind an ETA 6497?

Not if you stop when the crown stops. Winding has a firm end point; forcing past it can damage the mainspring.

Sources

• Monochrome: The history of the ETA Unitas 6497 and 6498
• Monochrome: Stowa Marine Original Arabic hands-on
• Deployant: Unitas 6497, the surprisingly versatile calibre

Keeping it running

• Wind it fully once a day, at the same time, until you feel the crown stop. Never force it past that point. Can you overwind it?
• A full wind lasts about 46 hours, so winding every morning keeps it running with time to spare.
• A watch winder can't wind a hand-wound movement, so it needs you instead.
• If it does stop, don't set the date between 9pm and 3am. Check if it's safe.

All ETA movements

Never let it stop

Watch Winder counts down the reserve of every watch you own and reminds you before one stops. It already knows the ETA 6497 / 6498: type your watch's name and the reserve fills itself in.

Manufacturer's published figure. Real reserve varies with the watch's age and service; check your manual.