An in deep view about the Benrus Type I Sterile.

Apr 17, 2010,16:14 PM

In the early ´70s some awesome watches born. Them are higly prized by collectors and endlessly copied/hommaged by other firms ... The Desirables Benrus Type I & II.


These amazingly durable and accurate watches have faithfully accompanied their owners on many dangerous reconnaissance and behind-the-line operations conducted in the hot and steamy jungles of Vietnam


Here is a recompilation of information about them.


Within the Benrus Type I versions we can find the Sterile variant and the Type I Class A, while within the Benrus Type II we can find the Type II Class A and Type II Class B.


So, you have 4 versions of these awesome Benrus. The most desirable is the Sterile version, due to its rarity among the others variants.

Firstly, the Type I Sterile (prototype, probably) and the Type I Class A were made. These highly-reliable Type I Class A watches were so successful that Benrus were contracted to manufacture other versions of the watch, namely Type II Class A and Type II Class B (which differed by having a 12/24 hour numerically indexed dial) to be used by members of the Armed Forces not participating in special operations

Some pics for these four versions, when you can see the differences:


Benrus Type I Sterile


You can see that the only marking is a serial number in the case back. No other markings are to be found anywhere on the watch.  


Credit pics: H. Seung.


Benrus Type I Class A.


The same watch that the Sterile version but with some markings in the case back.


This watch was designated Class A, which is essentially the highest classification awarded to military watches.

The writings in the caseback:


MIL-W-50717=the military specification
Type II Class A=Class A due to the fact that the hands and the dial of the watch are luminous.
Class B watches doesn´t use luminous material.
Benrus=the watchmaker brand must be writed in the back .
6645 - 22 - 1741=Fed / Nato stock No.
X7951=Maker´s Reference
DAAA25-72-CO656=Military contract code.
APR 1973=Date of delivery
SERIAL NO. / 0732=watch´s serial number asigned the day of delivery.
U.S.=United States Property


Benrus Type II Class A.


Credit pics: Christopher Moy..

Benrus Type II Class B.



Let´s go to an in depth view about the Sterile version Type I.


The sterile version of Benrus Type I is also known as the CIA model as it was issued to CIA maritime units along with NAVY Seals and Green Berets during Vietnam War.


These sterile watches, along with other Benrus dive watches, are non-magnetic to allow the wearer to work with magnetic mines underwater. And the "sterile" differs too, from the more common types I and II, by the fact of not having markings in the case back, only a serial number inscribed on the caseback…other than that, no other markings are to be found anywhere on the watch. Neither the military specification number, nor the issue date.


It is thought by many that the "sterile" watches were issued to covert operators. This lack of identification on the watch would maintain a level of deniability in the event the soldier was captured during a covert operation. Another less exotic (but probably more believable) theory regarding these "sterile" watches is they were unmarked prototypes issued for testing prior to regular production.


Certanlly, I think that we are speaking about unmarked prototypes, which makes them highly desirables.


These Benrus use an one piece case, Promethium PM-147 luminous substance (no Tritium substance), a rotating bezel to friction (no clicks) and a dial that only seeks maximum readability ....


The dial specifications:


Credit pic: BrandonS


In the flesh, these Benrus have an impressive dial, with an awesome readability, and a depth look. In this watch, in fact, less is more.


Many military equipments exhibit signs of well-regarded design philosphy, namely that form follows function. This is no exception to Benrus. The appearance of the dial, as you can see, is heavily borrowed from Rolex Submariner but with essentially no writing whatsoever - not even the manufacturer's logo - making the watch extremely legible, which is what all dive watches should strive for in the first place.


Another point that makes different these watches is the use of Promethium in the indexes. This PM-147 was used too in the Tornek TR-900. It´s quite unusual in the watches of the era, because quite all the diver watches made (Rolex, Omega, Blancpain, etc) used Tritium in these indexes.


Another point to be said is that it seems that there is no luminous marker at 12 o'clock position on the bezel. Well, you've guessed it wrong. The entire inverted triangular mark glows.


The hands have a "stair" configuration, as you can see in this pic…



Credit pic: H. Seung


The crystal is screwed down to the face of the case with an unique metal O-ring gasket. Screw-down crystal and one-piece case design allowed superior water resistance for these Benrus dive watches.

Well, to be sincere, these watches doesn´t have an one-piece case. Commonly referred to as one-piece case, the Type I and II, are in fact two-piece cases. The back is highly pressed so that is permanent. We can access to the movement through the front of the case, removing bezel and crystal. This system requires a two-piece stem, considered by some a weakness of this watch.

One pic is better than words…

These diver watches are true toolwatches, born to be a great company in extreme conditions. Ziggy Wesolowski, author of Concise Guide to Military Timepieces, reports the watch to have been tested to depths of 495 feet.

The black plastic coated bezel is somewhat puzzling since it has 0 to 11 marks instead of the more common 0 to 59 marks found on many dive watches. The graduated minute markers present between 0 to 4 were most likely used for measuring decompression times during dives. Anyway, this unsual bezel design have been carried on to later military watches, namely Adanac and Marathon watches.

The heavy steel case measures 47.5mm lug to lug, 42.4mm across the crown, with thickness reaching 15.3mm. Rigid strap bars are fixed to the case and takes a 20mm black nylon band. It has a screw-down crown with crown protecting shoulders that protrudes smoothly from the lugs. Probably, the most impressive thing in the general appearance of the watch is its true presence in your wrist, its strong look and the finish of the case: a kind of microbille case with an awesome grey finish.

One of the beautiful aspects found on this Benrus dive watch is the perfect dome shaped plastic crystal. It is very thick, about 3mm, and looks extremely tough.

Movement is Benrus signed 17 jewel automatic movement. One of the most unusual things with this movement is the fact that it has hacking seconds. It´s an Eta 2620 modified by Benrus due to the military specifications. It beats at 21,600 bph, and has 42 hours power reserve.

Zodiac Seawolfs of the same era were known to use these movements as well, which kept accurate time if properly maintained and regulated.

Here is a closed pic of the movement…


Hope you enjoyed this recopilation of information searched in the net about this true toolwatches. It has been my pleasure writing and making it…. But my pleasure is really stronger admiring it in my wrist smile


I bougth this watch to a collector from Haway and its last owner was an US military watchmaker in Vietnam.


Best to all my dear Purist´s Friends







All the info in this post is searched from the net.


1- Thanks to Nicolas who discovered to me this awesome watch and for his info about it here, in the Purist.

2- I have to credit the info and the pics to:


- g

- H. Seung page

- posts by Vegaban, in some spanish forums.

- Billy Schorr.


This message has been edited by E.J. on 2010-04-17 16:23:09 This message has been edited by E.J. on 2010-04-17 16:34:53

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Comments: view entire thread


Nice article!

 By: mkvc : April 17th, 2010-16:31
That's a lot of interesting information that is new to me.

Thanks, Mkvc!

 By: E.J. : April 18th, 2010-15:09
Always is a pleasure learn more about great watches. My pleasure doing it. Best Emilio


 By: sancerre : April 17th, 2010-16:48
That was indeed a wonderful article, thanks for the contribution. --Sancerre

Thanks Sancerre.

 By: E.J. : April 18th, 2010-15:11
Happy because you enjoyed this review. Best Emilio

Deep subject

 By: MTF : April 17th, 2010-19:25
Thank you for the "in-depth" summary of a very specialised subject. I tend to believe the prototype story for the 'sterile' . If you really wanted to have deniability, the operatives would be using equipment used by other sides e.g. China, USSR or East Ge... 

I'm more convinced of the exotic explanation . . .

 By: Dr No : April 18th, 2010-05:22
. . . as the intent was not so much for outright deception as to allow a captured Special Forces operative a plausible cover story as a member of another unit. I've been told of a first hand conversation between a Purist and a retired SAS operative. The f... 

Both explanations are interesting, and exotics at the same time...

 By: E.J. : April 18th, 2010-15:18
Protos or watches issued for covert operators (or both versions) must be possible, Art. By the way, them are iconic watches, IMO, with lot of soul and a great history behind. Best Emilio

Thanks, MTF..

 By: E.J. : April 18th, 2010-15:15
I think, too, that these watches were prototypes of the Type I Class A. As I said, a less exotic version but interesting at the same time. It makes more interesting and desirable these Sterile versions. Thanks for your nice words, it was my pleasure compi... 

Plausible deniability ...

 By: AndrewD : April 18th, 2010-04:45
Very interesting review, Emilio. I always enjoy learning something new about horological history. The hacking seconds are interesting too. I am thinking that I need a sterile F.P.Journe tourbillon. Then when my wife asks me: "isn't that one of those expen... 

Really thanks, Andrew.

 By: E.J. : April 18th, 2010-15:24
A great piece of History, indeed. These watches have a lot of soul. And, about you Sterile watch.... ... I think that you must try it. I´m sure that your wife will allow you to buy a sterile tourbillon.... come on, buy it! I will phone ... 


 By: aldossari_faisal : April 18th, 2010-05:33
and enriching, i just keep discovering other faces and side of watch collecting or loving. Thanks for posting. Faisal

Thanks, Faisal. Informative and interesting review...

 By: E.J. : April 18th, 2010-15:25
but this watches deserve it. Thanks for your kind words. BEst Emilio

very informative review thanks Emilio and an excellent example you have

 By: G99 : April 18th, 2010-13:12
i had a type 1 class A from 76 in my old collection, but i'm now going to look very very silly. i had another style Benrus dated august 1964. the very month i was born, and i let it go with all the others as i hadnt yet got the idea of collecting birth ye...  

A Class I from 1976.... this is my birth year, Graham.

 By: E.J. : April 18th, 2010-15:28
It´s a real pity that your sold this awesome watches. And the one from 1964 would be, now, a perfect watch in your awesome "I born in 1964" collection, Hermano. Don´t be silly, amigo... your enjoyed them! Thanks for your kind words, amigo mio Be... 

This watch talks to me very loud, Emilio.

 By: amanico : April 18th, 2010-13:30
The funny thing is that I have this review in stock for many months, now, and that I waited for the good moment to post it... I will wait a bit more. Back to your watch, it is in very good condition from what I see, and I'm very happy that you got it. It ... 

Thanks Hermano. I´m sure that your Autopsy would be perfect!

 By: E.J. : April 18th, 2010-15:34
Waiting it, hermano. I´ve compile some info in the net, and I´ve make a mix (un combinado, que se dice en España ) this watch talks to me very loud, too. Now, in my wrist, it has an awesome presence. I love it! Waiting for a nice sunlight t... 

Interesting read. Thanks for that. [nt]

 By: Davo : April 18th, 2010-18:18
No message body


 By: MattS : April 19th, 2010-00:40
Very interesting article!

Thanks, Matts. Not bad at all:))) [nt]

 By: E.J. : April 19th, 2010-05:56
No message body

Great Post!! Nicolas Make me discovers this amazing watchs too. About the "deniability" :

 By: pifpaf : April 19th, 2010-02:40
I know that French milititary undercover, and US or Soviet too, they use weapon and ammo that are not marked, for exemple, actually french COS, use ofently some Soviet weapon, for can't be specificely identified.... I think that work same for watchs. "It ... 

Thanks, Pifpaf.

 By: E.J. : April 19th, 2010-05:59
Nico is a Devil!. He gives us a difficult to beat virus Best, and thanks for your kind words emilio


 By: BDLJ : April 21st, 2010-04:15
So in this case, the way to ensure no one knows you're from the US military is to wear a completely unique watch, with no external markings, but a nice BENRUS on the movement.... I always thought the point of unmarked equipment was not to provide deniabil... 

An excellent post, Emilio!

 By: dxboon : April 19th, 2010-08:34
This really is a great series of watches! Military watches (and those modern versions inpired by them) have a certain tough-guy appeal that is just sexy and awesome. I love your watch, and enjoyed learning more about it from your wonderful post! Cheers, D... 

Daos, Why girls always love Bad Boys?? :)))

 By: E.J. : April 19th, 2010-13:16
I love your words: tough-guy appeal that is just sexy and awesome. Certanlly, sister, this watch has an awesome and strong look, an impressive appereance in your wrist, and it´s History makes it more desirable. Thanks for your, as always, kind words, my d... 

Bad boys are the most fun! :-)

 By: dxboon : April 19th, 2010-20:51
Ask your wife, Emilio! I'm sure she agrees! ;-) Have a wonderful week, my friend! Cheers, Daos

Yes, Daos...I´ve just ask to my wife...

 By: E.J. : April 20th, 2010-12:48
and she agrees with you. I´m so... I can´t change it! Have a great week you too, my dear hermana Best Emilio

very comprehensive review...

 By: Stefan : April 20th, 2010-04:04
... don't know much about this watch until reading this review. very enligthening and am impressed by your knowledge on these watches. should keep this watch safe and many thanks anyway! stefan

Really thanks, Stefan, for your kind words...

 By: E.J. : April 20th, 2010-12:54
I don´t have a great knowledge about them, Stefan, so I´ve make a mix of all the info that I´ve find in the net. By the way, thank to it, now I have a bit of knowledge Them are extremely rare and interesting watches. Pure passion and beauty... 

Very nice & good article.

 By: andy_s : May 4th, 2010-15:06
...perfect field watch, simple and functional - but taken to its nth degree. Great poachers watch!

Thanks, Andy!

 By: E.J. : May 5th, 2010-06:14
Certanlly, in this watch is sure that "less is more". Thanks again for your nice comments. best emilio

Old military Benrus watch

 By: kimby23 : August 14th, 2011-22:12
I was reading your post about the military benrus watch. I picked up a benrus watch that is very unique. It is 10 kt rolled gold plate bezel, stainless steel back. It however looks dramatically different then the military issues you have pictured. This pa... 

would really like to see...

 By: G99 : August 16th, 2011-02:02
would really like to see pics of this Kimby as its not one i've come across before. G

Benrus military.

 By: kimby23 : August 16th, 2011-16:14
My camera is just not that great so I apologize, Underneath the 12 marker is red, white and blue wing, directly underneath this is a square box for the day of week, BENRUS name, then hand dial, and another round dial with straight lines, appears to be a 2...  

and one more

 By: kimby23 : August 16th, 2011-16:24

Benrus military

 By: kimby23 : August 16th, 2011-16:34
I forgot to mention, in case you can't see from the pictures at the 3-6-9-markers there is merely just a raised gold dot. Mabey it is the generals watch or higher ranking officer watch. I really don't know.

hi Kimby,   in its...

 By: G99 : August 17th, 2011-01:25
hi Kimby, in its day it would have been a very nice watch, but the dial seems to be past its best now which is a real shame. it is a benrus, but it isnt a military watch IMO. firstly its gold or gold plated and i've never come across a gold military watch... 

a very nice and underrated collectible

 By: georgeszaslavsky : August 16th, 2011-02:48
Very nice post emilio. Ithink people should pay more attention to these watches because they are well made and collectable