Slide Rule Wristwatches (Page 4):
Japanese slide rule watches--Seiko, Citizen, Casio, Orient and Kentex


The first Seiko slide rule watch that I'm aware of was introduced in 1969. It's the automatic 6138 movement model 7000. This example was displayed on Edwin Datschefski's slide rule watch site where it was submitted by Kayvan.

Seiko apparently did this Rally style automatic SpeedTimer model 7017 6050 sometime in the 70s. (thanks to ebay seller restoredwatches for the photo)

Here's another early Seiko slide rule from Edwin Datschefski's slide rule watch site. It was submitted by Peter Holland. It's a Sports 150 model and I'd estimate it to be from the late 80s.

Seiko has had at least one Flight Computer in it's catalog for close to two decades now. Here's a Seiko Flight Computer from a 1993 catalog:

This Seiko SDWF75P1 is from Wayne's Watch World.

I've seen the Seiko SND253 also called a "Flightmaster" or "Aerospace Chronograph." It's exceptionally well priced, selling for as low as $100, and very cleanly styled.

Here's the Seiko 6M23-7000, to my eye, one of Seiko's less attractive models.

Seiko's SNJ017, is one the other hand, is quite appealing.

Seiko's 2007 Japanese catalog has three flight computers:

The Titanium SBDP005 seems to be a new addtion Seiko's 2007 Japanese line up:

Seiko's new for 2008 SNAB73P1 model is a very attractive watch. I'm not sure what the lever above the crown is for, but at least one person has christened it the "Zippo-Seiko." Apparently there are three other variations, the SNAB67P1, SNAB69P1, and SNAB71P1.

Also new for 2008 is the kinetic GMT model. This is one is SUN009


Pulsar is Seiko's mid-line brand. Pulsar's slide rule watches have been some of the most varied and innovative. Pulsar has produced a couple all digital models with a slide rule, some of the very few I'm aware of. I have a Navichron (the one on the far right in the photo) with the all analog display. Turning the crown changes modes. In chronograph mode the hour and minute hand start in the 12 o'clock position, so turning the crown to chronograph mode causes the hands to spin around like you are going back in time! The pictures here are from the 1992/93 TechGear catalog.

This is Richard Masso's Pulsar PYM001S (Originally submitted toEdwin Datschefski's slide rule watch site). Richard says, "Some quick technical notes about the watch that I like a lot. The stop watch (chronograph) has a digital tachymeter function. You can input the distance one will travel in miles or kilometers from 0.1 to 999.9 (miles or km) then when you run the stop watch and stop it, it will display the average speed over that distance traveled in miles/h or km/h. The compass is not an automatic one like current digital compass watches, it is a manual one that you use by the orientation of the sun. You set the hemisphere to be Northern or Southern depending on where you are, then you point the top of the watch (12 o'clock, you can see a small marking on the dial that says "SUN") to the direction of the sun, then you select which of 16 ordinal directions you are wanting to find (N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW, NNW) and the arrow in the center region of the dial will point to that appropriate location. It follows the same premise of finding the direction of North using the analog hands on a watch and the direction of the sun. The Pulsar (Model number is PYM001S, from their TechGear line at the time, originally retailed for $135 U.S. in 1992 to 1995). The watch was introduced in mid-1992 and discontinued in mid-1995. Many Regards from Austin, Texas USA."

This is my Navichron (and my first slide rule watch). It's on a replacement Citizen diver's strap. It's still running well 15 years on.

The Pulsar PJN057 is from the 90s as well.

Pulsar introduced it's Hyper Tech line around 2005. The models were an attractive analog-digital hybrid flight computer. I have the rubber strap version, and I like it quite a bit. It's heavier than you might expect but it sits well on the wrist. The slide rule accuracy is disappointing, 10 x 50 = 510 on mine. It uses two batteries, one for the digital display and one for the analog. The two displays are entirely separate. The digital display is a bit dim from some angles. It has a backlight which is nice, and a nice quality feel.

Pulsar's Tech Gear line was introduced around the same time as the hyper tech. They were somewhat overstyled analog flight computers.

Pulsar introduced 3 new flight computer models in late 2008. This is the model PF3781.


Alba is another Seiko brand. The AM7001X seems to be a different version of the Pulsar Hyper Tech.

Alba has a couple attractive automatic models with slide rules. On the left is the AL4041X and on the right is the AL4047X.

I bought my whiteface Alban AL4041 from Wayne's Watch World. I've always liked the nylon "zulu" bands. I put an orange 22mm 5 ring zulu strap on mine.

The Alba AF3A87X1 appears to be a version of the current Pulsar Tech Gear line.


While Pulsar is Seiko's mid line brand, Lorus is the brand used for Seiko's Cheaper watches. I got this Lorus QF047 for $10 on ebay in 2001.


The earliest Citizen slide rule that I'm aware of is Chuck Maddox's 1971 Citizen RecordMaster Rally Custom 21 Jewels. The outer ring is a non turning tachymeter bezel. Three additional rings are found under the crystal on the watch face. It has a top left Citizen "CTZ" signed crown that bi-directionally turns a 10 thru 90 indexed ring / slide rule bezel under the crystal. Like the Camy Rally King on the preceding page this watch is somewhat specialized as it only has one logarithmic scale which rotates around a fixed time scale. It would be useful only for making time-distance calculations (presumably of interest to rally divers) and not generalized multiplication and division problems.

Here's another early Citizen Rally Style watch that's a dead ringer for the Camy Rally King. Shukri sent this picture to me, sorry no date or model info.

Richard Smythe sent in this excellent photo of a Citizen cal. C046 Aerochron circa 1993. It features a sensor that measures atmospheric pressure and altitude.

Goran Jemric of Zagreb, Croatia sent this photo of a Citizen Promaster cal.3510 to Edwin Datschefski's slide rule watch site.

Citizen's Wingman is a popular flight computer that has appeared in several forms since it's introduction (around 1990?). These are from the HME watch 1994/95 catalog.

Some more Wingmans from a 1996 catalog.

My favorite Wingman is the cleanly styled Wingman VI which came in at least a couple variations (shown below). I should have picked up one of these when they were still in production.

Another of my favorites is the cleanly styled Titanium Navihawk which I believe was intended for the Japanese market.

While most of Citizen's slide rule watches have an aviation theme, not all do. Here are a couple of attractive models from an undated (early 90s?) catalog. The "racing" model with the rubber strap on the right appears to be a rally style watch with only one logarithmic scale that rotates around a fixed time scale.

Citizen has produced at least two different Blue Angels models.

In 2005, Citizen introduced the Nighthawk which, unusually for a Citizen flight computer, did not feature a chronograph movement.

Here are four radio controlled models from Citizen's 2007 Promaster (Japan) catalog.

The two on the left below are also radio controlled (sometimes called "atomic time") Skyhawk AT models from Citizen's 2007 US catalog. They are just slightly different in appearence from the Japanese market versions, and to me eye seem comparitively overstyled. The one on the right is an earlier, non atomic time version of the Skyhawk, also from the 2007 US catalog.

New for 2008 is the Promaster SST. This one is model JW0030-55E.

Here are some new models from Citizen's Japanese market 2008 Promaster catalog.

Q & Q

Michael B. Keller sent in this pic of his Q&Q "Rallye Timer" from the "Exclusive Collection" to Edwin Datschefski's slide rule watch site. He says, "Q&Q is made by CITIZEN. My watch has an OS-81 movement from Miyota, featuring an alarm function. The slide rule has markings for flight calculations, like conversions fuel lbs-kg, fuel gal-ltr,, ft/sec-mtr/sec, flight distance, rate of climb/descent etc etc... as well as the usual calculations you can do with a slide rule (multiplication, division,...). The chronograph can be used to time events from 1/10th sec up to 12 hours. This very nice pilots watch is available in all of europe for EUR 99,- You can choose black, blue or white dial. The slide rule is a litte bit hard to handle, because of the large distance between the inner and outer ring, which makes reading it a bit difficult. Still, itīs a very nice, true pilots watch!!! Greetings from Germany, Mike." See Mike's full review at


Casio hasn't produced the range of slide rule watches that Seiko, Pulsar and Citizen have. Those they have produced though often offer a lot of watch for the money. Casio seems to have produced three groups of slide rule watches: The DW-400,401,402,and 403 in 1992; The DW-7000,7100,7400 and 7500 from around the same time, and Casio's current (2007) analog models shown below. Here's the one I believe is the first, at least in terms of model numbers, the DW-400 "Tachy Meter." The DW-400 and DW-401 use module 905. (Photo from

Here's are couple similar models, the DW-401 Surfing Timer and DW-403 Sky Walker. The DW-402 Surfing Timer seems identical to the DW-401 (at least to my eye), except the DW-402 and DW-403 use module 906. (Photos from Vintage Casio Watch)

This one is the DW-7100 also from the early 90s. The DW-7100 and DW-7500 are the same watch excepts for bands. The 7100 came with a metal band and the 7500 had leather. They all share the module 913 and, interestingly, also share the same manual as the 905 and 906 module slide rule watches, so they were probably introduced at the same time. There isn't much information on these models, I suspect that they may have been marketed primarily outside the US. The watch pictured was purchased in Europe in 1991. (Thanks to Greg for setting me straight on the model numbers, Picture courtesy

Here's a nice photo of the DW-7000 (or DW-7400) on the right. The DW-7000 was the metal banded version, and the DW-7400 originally came on a leather strap. The one on the left is either a DW-7100 or DW-7500. (Photo courtesy of Mike)

Here are a few recent Casio models. From left to right, the EF518D-1AV, MTP4500D-1AV, and MTP4700D-2AV. I have the MTP4700D and it's a nice watch. The slide rule is a bit hard to read as there's a small gap between the dials, and the two scales of the bezels are in different planes, but for the $40 I paid at it's a very good deal.

In Europe, Casio's models are offered with differenct colors and bands. Here's the MTP-4500L-1AVEF with a leather strap and silver bezel. From this photo, the gap between the two scales and the different angles of the two scales are apparent.

In 2009, Casio introduced the attractive Ediface model 527L-1AVDF. Nanok sent me a link to a review he has written that mentions the inner rotating slide rule is accurate with no slack in the winder. He also took this picture.


The first Orient slide rule model I'm aware of is the titanium Military model that was introduced around 2004. I had a titanium Orient Military automatic model, but I don't think I had a good example. I did like the titanium finish, but the automatic movement sounded unpleasent. It made sort of scraping sounds when it was wound, and I could actually feel it winding on my wrist. Even worse, the crown had a habit of coming out while I wore it, so the time was frequently off.

There is a whole slew of slide rule models in the current (2007) line up. The newer Military automatics are styled a bit differently:

This one is a quartz chronograph model CTD0G001B:

This is the Orient Multi-eye automatic:

Here is another quartz chronograph:

Orient also produces a very attractive skeletonized automatic with a slide rule:


Kentex is a Japanese watch company that was founded in 1989, but didn't start making watches under it's own name until 1997. It's notable for supplying watches to the Japan Self Defense Forces (JSDF). They have several models in their current (2007) line up that feature integrated slide rules, but unfortunately few seem to be sold outside Japan. All of the slide rule watches have the designation "SkyMan." Here's the JASDF SkyMan:

This model is the SkyMan Navigation.

Much like Breitling, Kentex offers an optional small GMT watch that fits at the top of the band:

The SkyMan "Blue Impulse" edition:

The Skyman IV is one of the few Kentex watches regularly seen for sale on ebay. I've also seen it listed as the "Tufina Black Mamba", "Luning Fliegeruhr" and the "Estana Skymaster." The models sold on ebay are probably cheaper versions that are assembled outside of Japan, since they typically sell for less than half of what Japanese vendors charge.

The SkyMan 4 PRO has a Valjoux 7750 automatic movement:

Page 1: Introduction, History and Breitling slide rule watches

Page 2: Ollech & Wajs, Sinn, Hacher and Heuer slide rule watches

Page 3: Other Swiss slide rule watches

Page 4: Japanese slide rule watches--Seiko, Citizen, Casio, Orient and Kentex

Page 5: Other slide rule watches

Corrections, comments and additions to Art Simon