The following is a great article by H. Seung that discusses the Benrus "Type" watches and the different variants. It is a very good and informative read!! Enjoy!
******************************************Benrus Type I Class A Military Dive Watch
Review and images by H. Seung
During the final years of the Vietnam conflict, members of UDT-SEAL, Green Berets, and Special Forces were issued with the ultimate military dive watch the U.S. Military have ever issued: the Benrus Type I Class A
dive watch. 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. The particular Benrus dive watch reviewed here is a 1976 issue of the Type I Class A model with full military inscriptions on the caseback which was the model commonly issued to UDT-SEAL members.
The Type I Class A dive watch has, what I would consider, the perfect dial for military dive watch, field-proven case design, and the only U.S. military issued watch to feature an automatic movement. Not only that, it was made under a military specification of its own, namely the MIL-W-50717 specification. As far as I am aware of, no other watch besides the Benrus was made under that particular specification. Also, the watch was designated CLASS A, which is essentially the highest classification awarded to military watches.
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.
Luminous material, probably tritium, is applied to the hour indexes, as well as the minute, hour, and second hands. They illuminate like a charm after being exposed to a secondary light source. From the photos, it looks as though 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! It's no technical marvel, but still it's like finding one of those neat concepts hidden among various military equipments from time to time.
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. My theory is that it was probably used to reference Zulu time in combat missions. 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
watches, so I guess it had some purpose after all.
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. One-piece case design helped the watch achieve necessary water resistantance required by the nature of underwater activities conducted by UDT-SEAL teams. Ziggy Wesolowski, author of Concise Guide to Military Timepieces
, reports the watch to have been tested to depths of 495 feet.
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.
Anyway, since the watch utilizes one-piece case design, you'd have to remove the plastic crystal to access the movement. Here's a photo of the movement taken out for cleaning and lubrication by my watchmaker:
It's a 17 jewels ETA automatic movement, signed ``Benrus Corp'' on the automatic winding disc. It has the desirable hack feature. My watchmaker was quite surprised to see such a fine movement installed on a Vietnam-era military watch. He also mentioned that it was one of the better movements supplied by ETA but were no longer available. Zodiac Seawolfs of the same era were known to use these movements as well, which kept accurate time if properly maintained and regulated. Here's a closer shot of the movement:
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. It is rumored that Benrus made a small number of civilian version of the Type IIs with ``Benrus'' written on the dial but I have yet to see one personally. Below are scans of Type II Class A and Class B that were recently auctioned on e-bay:
Benrus Type II Class A
Benrus Type II Class B
There exists a sterile version
of Type I Class A that has no specification markings whatsoever on the caseback other than a serial number identifying the watch. These were mostly issued to Green Berets, Special Forces, and CIA members who were engaged in behind-the-line operations and other covert missions. The watches and equipments they used had to have no trace of evidence indicating the country they were serving.
Sterile Version of Benrus Type I Class A
Finally, before I forget, let's go over the military inscriptions found on the caseback of Benrus Type I Class A dive watch...
MIL-W-50717 TYPE I CLASS A BENRUS 6645-00-477-4210 X7952 N00104-76-D-2127 SEP 1976 SERIAL NO. 1035 U.S.
An educated reader would have noticed that these are NATO codes describing that such and such wristwatch was issued in September 1976 by the U.S. government and was made according to MIL-W-50717 specification. I still don't know what other codes mean...
Well, I hope you enjoyed this long review on one of the finest military dive watch produced by the United States of America. As you might have guesses, it's my favorite military dive watch. Unfortunately, as sad as it may sound, this watch does not belong to me. If you have one lying around the closet, please let me know!
Here is the original content... http://www.50717.com/us/benrus-1-76.html