Benrus MIL-W-3818B
Vietnam Era Service Watch

Buyers and collectors today have an exceptionally broad range of modern watches to choose
from that, in one way or another, are styled on military issued service watches.
Of special interest to collectors are those watches that were authentically issued by a nation's
military to an active serviceman.

Benrus MIL-W-3818B service watch, issued by the US government to a soldier in the mid-1960's.
Acquired out of an estate sale for an old vet.

This old watch has had a long hard life, & it shows.

The case & crystal are scuffed & worn.

This watch uses a split stem system where the stem is in two parts & couples together in the middle. Separating the stem in two then allows for the watch movement to be removed from the case.

This watch has lost its male half of the stem & the crown along with it. A sadly common problem for this type of watch, & one that typically results in the watch then being abandoned indefinitely in the back of a junk drawer.

The watch does not appear to be running, but hard to tell in this state without having a crown to work with (maybe we'll be in for a surprise later on...).

1964 service date. Don't have any way of knowing if this piece was on tour in Vietnam, but the calendar lines up.

'MIL-W-3818B' is the US Govt specification for the military issued service watch of this era.

This watch was produced by Benrus. Other manufacturers such as Hamilton & Wyler also provided service watches built to the same spec.

Collectors today are intensely interested in the minute variations from one manufacturer's service watch to the next.

Disassembly

A carefully measured puff of air in through the stem tube to pop the crystal free.

And with the crystal off the watch then starts running.
Apparently the seconds hand was touching the underside of the crystal. This is enough
resistance to foul the operation of the movement.

Seeing the movement running at this stage is encouraging, as this gives an early indication that the movement is intact. Although it doesn't speak too highly of the last operator to have had this watch opened up on the workbench & who then put it back together in a non-running state...

These watches came from the factory with luminous compound ("lume", in watch-speak) applied to the hands but not to the dial. Will commonly see old service watches that have had lume compound added to the dial later on, & that's what we see here on this piece.

However, it looks like a pretty amateur application in this example, 6 gets a big double helping & 5 gets nothing...

Now there's a decision to make about what level of restoration to apply on this project.
Normally I would prefer to do a sympathetic restoration; try not to add anything, try not to remove anything.
But, some other guy beat me to it this time, so now need to figure out what it means to clean up this piece starting with the dial condition.

Can continue on with the movement restoration while pondering what kind of mark I'm going to leave on this watch once it's done.

Watchmaker's dial paper under the hands & plastic protection over top. Want to avoid doing anything to mar the dial (further) while removing the hands.

Dial screws on the side of the movement to capture the dial feet, securing the dial to the movement.

Dial side of the movement.
Not seeing anything missing or broken, so far so good.

This slips freely on the cannon pinion, & the only thing holding it in place in normal operation is the presence of the dial. We'll remove this one component from the dial side now (which would otherwise happily just fall off on its own).

The rest of the motion works (moving the hands) & keyless works (winding & setting) hardware can wait until later.

Hour wheel

The watchmaker side of the movement.
Looking a little bit grimy, but otherwise in OK shape. We may get a working watch out of this project yet...

Pallet fork.

Each oscillation cycle of the balance wheel unlocks the pallet for a very brief moment, during which the mainspring is free to drive the wheels (gears) of the going train forward by one tick. The balance wheel is in constant motion, but for most of the time the going train is stationary.

Ratchet wheel

The ratchet wheel turns the mainspring barrel arbor when the watch is being wound.

In this Benrus DR 2F2 movement the ratchet wheel overhangs some of the wheels of the going train, so removing this now will make disassembly of the going train easier later on.

Click & click spring.

The click enforces the ratcheting action of the ratchet wheel, allowing the ratchet wheel to turn in one direction to wind the mainspring, & then preventing the mainspring from unwinding by holding the ratchet wheel in place once the winding action has ceased.

Crown wheel.

The crown wheel is driven by the winding action via the crown & stem, & in turn drives the ratchet wheel to wind the mainspring.

Barrel bridge & mainspring barrel underneath.

Train bridge & the wheels of the going train underneath.

Fourth wheel

Third wheel

Escape wheel

Mainspring barrel

The going train.

The gearing ratios of all the wheels of the going train combined with the frequency of oscillation of the balance wheel is what provides the timekeeping function of the watch.

Mainspring barrel

The phenomenon of you & everyone around you being perpetually surrounded by microsecond-accurate network time is a recent development in the idea of timekeeping.

Up until the late 20th century, if you wanted your watch to be in sync with your partner's, then you both needed to manually set your watches to an agreed reference. This is where the 'Hacking' feature makes itself useful.

On a hacking watch, pulling out the crown into the setting position stops the movement & the hands while the time is being set. If everyone in the party pulls out their crown & "hacks the time" when their second hand is at the 12 o'clock position, then everyone can start their watch running again on the same signal & all the watches will be in sync to the second.

On a watch without the hacking function, the second hand continues to turn while the crown is pulled out into the setting position. The best a group of people could do in this case would be to synchronise their watches to the nearest minute (not good enough for soldiering...).

This movement started out life as an ETA 2372, modified with the addition of a hacking function which then makes it a Benrus DR 2F2 movement.

When the crown is pulled out the hacking lever turns & the hacking pin is pressed against the balance wheel, & this 'hacks' the watch.

The hacking lever looks rather crude in form & finish compared to the rest of the parts native to the original ETA 2372, but it meets the MIL-W-3818B spec, & that's all that is required of it.

In the 2nd half of the 20th century wristwatches designed for a specific purpose or profession came into being. Among watches designed for science, engineering, & soldiering the hacking feature became a requirement. This feature then came to be considered a mark of superior quality, & manufactures would try to distinguish themselves among their lesser competitors by promoting their superior watches with "Hacking Seconds".

Dial side of the movement

Setting wheel cap

Minute wheel, intermediate setting wheel, & setting wheel

Setting lever spring

Clutch lever & spring

Clutch, winding pinion, setting lever, setting lever screw, & stem
(the stem has issues...)

The jaw on the female end of the split stem is bent out of shape.
This likely contributed to the loss of the male half of the stem & the crown along with it.

The ETA 2370 base movement was a common & popular movement throughout the 1950's & 60's, & there are still original spare parts available today.
(For some parts, but not all, as we will run into later on...)

Lower balance jewel assembly

Lower escape wheel cap jewel

So why would the watch be constructed with a cap jewel for the lower escape wheel pivot, but not for the upper pivot on the other end?
In a conventional watch design if you have the all the regular allotment of hole jewels, cap jewels, & pallet stones then these would normally add up to 17 jewels. This then became a kind of shorthand for a fully implemented, good quality movement. It is absolutely possible to make a decent quality, reliable watch movement with fewer jewels, but then the marketing implication is that corners were cut to make a budget watch.

The ETA 2370 base movement was likely an iteration from an earlier 15 jewel design, but ETA needed to find a place to stick in a couple of extra jewels in order to market the watch movement as a fully grown up "17 Jewel" movement.

(Even if the usefulness of the placement of those 2 extra jewels doesn't really add much practical benefit...)

Many of the screw heads show some corrosion. Certainly due to moisture penetration inside the case.

These old watches were barely watertight when they left the factory, less so after every day of knocking around under field work.

Light polish with some 3000 grit, just to get them looking a little bit nicer.

Upper balance jewel assembly

Installing the balance back onto the mainplate prior to cleaning. Keeping the balance secured in its regular home between the mainplate & the balance cock will provide protection for the very fragile hairspring & balance staff end pivots during the cleaning process.

(Nice shiny screwhead!)

The Benrus DR 2F2 is fundamentally a pretty simple movement. You get 3 hands, hacking function, & that's it.

Doesn't fill up very many cubbies in the parts tray.

In to the ultrasonic for 2 cycles of cleaning & 3 cycles of rinse.

Reassembly

Applying a small drop of oil to the escape wheel lower cap jewel.

Lower balance jewel assembly

And the same treatment for the upper balance jewel assembly

Minute wheel & keyless works

That's as much as we want for the dial side for now.

Over to the watchmaker side & starting with the hacking lever.

Stem in, hacking lever retracted.

Stem out, hacking lever extended.

Mainspring, barrel arbor, & a small amount of grease applied to the upper & lower barrel interior.

Something military quartermasters learned fairly early on was that you don't outfit a soldier with a fine quality Swiss watch (because they will trade it for beer at the earliest opportunity...).

So, from around the 1880's onwards the objective became to design & build the service watch that was accurate enough for coordinating tactical groups, robust enough to survive in the field, & cheap enough to not be worth trading away.

The going train of wheels

Second wheel

Mainspring barrel, which also incorporates the grand wheel (the teeth milled into the perimeter of the barrel)

Escape wheel

Third wheel

Fourth wheel

Train bridge & barrel bridge

The MIL-W-3818B specification & this Benrus DR 2F2 are one stop along that evolutionary path for the service watch.

At the time, these watches were regarded as a disposable tool, & treated accordingly. The expectation was that you would use it until it broke, then throw it away & get a new one.

Crown wheel, click, & ratchet wheel

Click & click spring in place

This is a nice design, from the watchmaker's perspective, as the click spring here is not under tension unless the watch is actively being wound & the ratchet wheel is turning.

In many movement designs the click spring is preloading tension on the click, & is hence poised to launch itself into orbit while waiting for the slow watchmaker to get it covered up & captured by the ratchet wheel.

A little bit of pitting & corrosion still visible on the crown wheel & ratchet wheel, but these parts are still very serviceable.

Today collectors & historians regard these service watches as artifacts from the 60's, the Vietnam war, & the lives of the servicemen who carried them.

Back then they were seldom looked upon as something worth saving, & because of that lamentably few survive today.

It would be a good feeling to get this old watch up & running again.

Pallet fork & pallet bridge

The end facets of the pallet stones require their own unique type of lubricant.

In earlier restoration projects I have typically applied this prior to installing the pallet fork, but the very talented watchmakers that I like to watch on YouTube recommend doing this application with the pallet in place (less chance of accidently smearing the lubricant around to other surfaces while handling the pallet).

Giving this method a try, but that is one tiny little target...

The moment of truth, will find out now what kind of a job we did on the rest of the movement...

Success

We have a working movement, but the work is not yet done for this watch.
Now on to the cosmetics work for the dial & hands.

Gently scraped the grotty looking old lume off of the dial, but this still resulted in the original paint finish for the hour index marker getting lifted off along with it.

Trying some flat white acrylic model paint to restore the lost markers.

it's not perfect (and it never will be), but I think that's an improvement on the old state of the dial.

The hands have an odd mix of old coatings, & the old lume compound contained inside the wireframe of the hands has degraded & fallen away, likely a combination of age & moisture exposure.

Fiber pen to gently scrub out the old lume.

Gentle polishing with some 2000 grit to get most of the way down to bare metal.

Ready for a thin coat of white paint, to hopefully match what the hands looked like when they left the factory.

Fresh lume to finish off the hands.

The lume compound is mixed with acrylic varnish to about the consistency of latex paint. The liquid surface tension makes the fresh lume compound conform to the shape of the wireframe while curing.

That's looking better

Before we can complete the final assembly, need to acquire a replacement for the missing half of the split stem.
Since these are the pieces that commonly go missing they are also the pieces that have long since run out of replacement supply. Time to improvise...

Start out with a complete single piece stem as a donor part