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Seiko Epson Caliber Yn55a

S. Epson Caliber YN55A

Seiko Epson Caliber Yn55a

Brand S. Epson
Caliber Number YN55A (aka YN55)
Movement Type Automatic, self-winding mechanical
Diameter 27.4mm
Height 5.32mm
Jewels 22
Vibrations Per Hour
21,600 bph
Anti-Shock System Seiko Diashock
Power Reserve
40 hours
Hand Windable?
Yes
Hacking? Yes
Lift Angle 52 degrees (unconfirmed)
Hand Count
3
Hand Sizes
1.50mm / .90mm / .20mm
Functions Central hours; central minutes; central sweeping seconds; date indicator at 3:00
Hacking Seconds?
Yes
Country of Manufacture Made in Japan
Known Models Vostok Europe Expedition North Pole-1, Aries Gold 9010 (Add your watch to the comments below…)

The S. Epson caliber YN55A is essentially an unbranded version of the Orient caliber F6722. It is a self-winding automatic movement with 22 jewels, also featuring hacking and hand-winding functionality. These movements are manufactured in Japan.

YN55, YN55A, YN55B, YN55C, etc…

The letter at the end of YN55 indicated the iteration of the movement. YN55 is the base caliber number and YN55A is the first version. As of this post, there is only a YN55A iteration, therefore, YN55 is the same as YN55A.

Accuracy:

Accuracy of the calibre YN55A is said to be within -25 seconds to +35 seconds per day. These ratings are based on the watch being at room temperature with the mainspring fully wound and the dial up position. Official documentation from Orient suggests that deviations from the accuracy claims should not be regarded within one day but within a one week period of results.

From the Orient manual:

“In order to maintain the watch’s accuracy, we recommend wearing the watch at least 8 hours a day.”

Power Reserve:

The YN55A has a power reserve of 40 or more hours. Winding the crown 30 times will wind the spring fully and achieve full power reserve.

Setting the date:

To set the date on your S. Epson YN55 powered timepiece, pull the crown out one click to calendar setting position. Turn the crown counterclockwise to advance the date. Avoid setting the date between the hours of 8:00pm to 4:00am.

In Orient Watch USA’s own words:

“After years of development, Orient had perfected a new watch caliber, the F6922 (aka S. Epson YN55), an automatic, hand-winding and hacking movement. It was built to succeed the oft-revered 46943 movement, which had powered Orient watches reliably for more than 40 years. Among the first watches to be powered by the new in-house caliber were the Mako II and the Ray II, which were released in April 2016.” –6/28/16

Examples of watches with this caliber:

The YN55A example pictured below was found in a Vostok Europe Expedition North Pole 1 watch. Image submitted by David R.

Seiko Epson Caliber Yn55

Additional Resources:

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L a r r y
L a r r y
2 years ago

Does Seiko own Epson or the other way around?

David R
David R
2 years ago
Reply to  L a r r y

This should answer your question. It was finally answered for me too

daniel
daniel
2 years ago
Reply to  L a r r y

seiko acquired epson in 1985

daniel
daniel
2 years ago
Reply to  L a r r y

but mostly if not all seiko’s movement with malaysia etch were made/assembled by epson precision

JadeGeminiM390
JadeGeminiM390
1 year ago
Reply to  L a r r y

So the way to look at it is step siblings. One one side your have Seiko Time Instruments. If you follow up that bloodline it evenly goes up to the top at Epson-Seiko Company, which was a merger of sorts in the 80s. If you continue to follow the Epson bloodline down the other side, you get to Orient, which is owned by Epson. So this Epson is a Orient movement, but unbranded. Kind of like how the NH35/36 is a Seiko 4R36 but the unbranded version. So this is made in Orient’s factory, separate from Seiko’s. It’s a different… Read more »

Jem
Jem
2 years ago

does this have indirect second drive similar with miyota 8xxx or a direct second same with seiko nh35/36?

Standard Date
Standard Date
2 years ago
Reply to  Jem

Direct drive seconds, just like all Orient movements that I know of from the last 20 years.

trackback
Orient Caliber F6922 Watch Movement | Caliber Corner
2 years ago

[…] Epson caliber YN55 (YN55A) appears to be essentially an F6922 without the Orient branding, for use in non-Orient watches. The […]

Greg Mohney
Greg Mohney
1 year ago

The Pagani “Black Bay” homage PD-1671 features an Epson-signed YN55A movement.

J.B.
J.B.
1 year ago
Reply to  Greg Mohney

Really? I just ordered one about a month ago and it has NH35 on the rotor. Strange.

Greg Mohney
Greg Mohney
1 year ago
Reply to  J.B.

Yeah, interesting… dunno!

Darth
Darth
1 year ago
Reply to  J.B.

Hmmmm?

I_Am_Watcher
Member
1 year ago
Reply to  Greg Mohney

Some Pagani (and other Ali brand) model listings offer a choice for 3 types of movement: NH35, YN55 or Miyota 8215, I’m guessing because they aren’t available in equal quantities or to cut costs. They all come with a different price tag, with Miyota being the cheapest and NH35 being the most expensive. I can imagine they sent you a watch with the wrong movement.

PD-1671b.jpg
Greg Mohney
Greg Mohney
1 year ago
Reply to  I Am Watcher

Ahh very interesting! I got mine from Amazon, no choice in movement. So I reckon that’s what they had! Thanks for the info.

I_Am_Watcher
Member
1 year ago
Reply to  Greg Mohney

They probably ship them out with random movement at Amzon. Ps: 1 thing I always point out: if you have screwed removable links, like these PD-1671 have, make sure to secure the screws after you sized the bracelet. You can use Loctite (pick the right one!) but that’s expensive, I’m a cheap bstrd so I use cheap clear nailpolish. If you don’t secure the screws they will eventually come loose and the watch will come off when you least expect it, like in the middle of the street. I’ve read a lot of reviews where this happened and people were… Read more »

J.B.
J.B.
1 year ago
Reply to  Greg Mohney

I got mine from Amazon as well. I could have probably gotten it cheaper on AliExpress, but I wanted to have the assurance of a quick return if I didn’t like the watch. It’s amazing the quality that can be offered for such a good price. Finishing is top notch and it’s running about +4spd.

Greg Mohney
Greg Mohney
1 year ago
Reply to  J.B.

Haha I know! I do the same thing. People use Ali Express to “save money” but… to me, sending the watch back to China seems like such an unbelievable hassle. I just always use Amazon. It does limit my choices though, and it’s more expensive. But if something goes back, so easy to return. No haggling.

Vitor
Vitor
1 year ago

I have an Orient with the so-called YN85 caliber. Should I assume it is the successor of this YN55? It’s embarked in an Orient Brazil watch and I can’t find any information about it in any place…

Das
Das
1 year ago

San Martin SN020B limited production run contains this movement. I hope its a solid movement… I just ordered one.

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