Towards the end of the 1980’s three different manufacturers, Sinn, Tutima and Precista released low profile 200m rated divers watches, all of which used essentially the same, very distinctive case housing an ETA 955.114 (latterly 955.112) quartz movement.  Both the Sinn 815 and Tutima 513 versions were sold as mainstream divers watches

 Unattributed images from Google

but the Precista version was distributed only as an issued watch to the Royal Navy between 1988 and 1989.

Photocredit: http://scubawatch.org/precista.html

A re-edition of the Precista also appeared a few years ago in a Fricker made case housing either a quartz or automatic movement and sold and marketed by Timefactors in the UK.   The issued Precista watches are hugely collectable and these days can fetch serious money (£ four figures) but for an order of magnitude less, you might take the approach I’ve taken on this latest little project.

We start this one with another Ebay purchase, this time described only as a ‘Divers watch case, 2 tone, black and silver’.  It does not take much in the way of detective skills to notice the similarity in the case shape to the threesome above

Photo: Ebay seller

An offer made and accepted, I soon had what was clearly a very nice, unmarked new old stock case in my hands.

The case size is modest at 37.3mm across the bezel and a little over 42mm across the case, including the substantial crown but in terms of thickness, it’s an exceptionally low-profile watch considering its depth rating.  You can appreciate quite how low in profile it is in this side shot next to the Hellas mid-size dive watch I wrote about a couple of posts back:

In order to convert this from an empty vessel into a watch I would now need to source a movement, a dial and a set of  hands. The movement choice is straightforward:  The Royal Navy Precista would originally have been fitted with an ETA 955.114, the Sinn and Tutima probably with its successor, the 955.112.  These are quite nice 7 jewel quartz movements notable in particular for very small stem height of 1mm (the distance from the dial side of the movement to the stem hole).  The 955.112 is still readily available for modest cost or alternatively, and cheaper still, its lower spec 3 jewel replacement, the ETA F06.111.  One other obvious option is the Ronda 715 (a bargain at less than a tenner) a variation of which was used in the quartz version of the Timefactors re-edition.  For this project though, I opted to stick as closely as possible to what would originally have been fitted and so ordered a 955.112,

plus a white on black date wheel to maintain the stealthy look of the PVD case.  The next job is to decide on the dial because this then influences what style of hands to go for. As the movement is from ETA, the dial choice is potentially quite wide – any dial designed to fit the ubiquitous 2824-2 automatic movement will fit the 955.112.  The problem though is one of diameter.  Most of the dial styles I had in mind were only available from third party generic watch parts companies – which is good because I did not want any branding – but pretty much all of these come in at 29 mm across the beam and the dial aperture of this case is only 28mm.  Failing to find anything of small enough diameter, I opted instead to buy a 29mm dial and resolved to find a way to reduce its diameter to fit the case.  Here then is the dial I bought:

Photocredit: Ebay seller

You might notice that there is plenty of excess beyond the minute ticks on the periphery of the dial suggesting I would in principle be able to reduce it by 1mm in diameter without encroaching on the main real estate of the dial.  You can appreciate the problem perhaps by viewing the dial seated in the rear of the case, its edges overlapping the lip in the case when in fact it should be seated within the circumference of the lip.

Of course, it’s all very well conceiving of this as a plan; it’s quite another thing to accomplish it without damaging the surface of the dial.  I ended up giving this a lot of thought before tackling it – several weeks in fact – but ended up with a strategy that I thought could work.  So, in order to do this properly, not to bodge it, I took the view that the only way to turn the dial down was to mount it somehow into a drill chuck, spin it up and sand away the outer 0.5mm against a piece of fine grade wet and dry sandpaper.  Attempting to do it by hand somehow was out of the question, not least because in order to do that you have to rough handle the dial and that would certainly result in damage.  How then to mount the dial?  I consulted the mechanical engineering workshop at work for advice but they are used to working with raw materials and not a finished product.  The engineer there did suggest making a Teflon support to clamp the dial through its centre hole, and in fact we did try this approach with a spare dial but ended up with a nice circular mark at its centre.  So I was on my own.  My eureka moment came when I realized I had a spare non-working ETA quartz movement, the main plate of which I could use as my mount.  With the dial secured by its feet to the holes in the main plate, all I needed to do was fit the main plate to a threaded bit and we were in business.   With all the ancillary components stripped from the spare movement, I drilled out out the centre hole and then secured the main plate to a shaft taken from a Dremel sanding wheel.  The securing screw needed to be sanded down a bit to give sufficient clearance to the dial, but this looked like it would do the trick.  Here’s my improvised mount:

and here it is with the dial mounted, ready for action:

I confess to having had visions of the dial detaching itself mid-spin and shooting off across the room but in fact the reduction process worked really well: no zinging dial; no severed carotid; and more importantly not a mark on the dial other than the nice shiny finish to the edge of its exterior circumference.  A quick test fit to the case reveals the lip previously hidden in the before shot above.

We haven’t talked yet about the hands.  The problem with working with a quartz movement is the hand hole sizes are different from those which fit the common ETA automatic movements.  The latter require 1.50/0.90/0.25 mm hand holes (hour/minute/seconds) but the hand sizes for ETA quartz are 1.20/0.70/0.20 mm and the choice of  generic hands in this fitting and in styles that would work with my dial choice is limited to rather humdrum generic stuff that in this application would not do the project much justice.  Some more thinking, a bit of research and I realized that many of the quartz Omega divers watches were fitted with ETA derived movements with potentially the same hand sizes.  This triggered a vague memory of some quite cool looking hands with a sort of Ploprof vibe fitted to early 90’s mid-size Seamaster 200m divers watches.  The watch I was thinking of was the 396.1051, fitted with a 1441 movement which is basically an ETA 255.561.

Catalogue shot from Google images

See what I mean?  We’ll get back to these in a moment when it comes time to fit them.

At this point in proceedings, we’ve got everything we need to put it all together, starting with that white on black date wheel.  Here’s the 955.112 movement as received, replacement date ring to one side

Whip off the standard date ring, and on with the new

Next up, let’s try that slimmed down dial for size

Looking good.  On with those tasty Omega hands

and I start to have a bit more faith that this is going to work.  Needless to say the lume on the Omega hands completely overpowers the rather feeble stuff on the aftermarket dial but the dial is otherwise so well executed that I forgive it that small flaw.  Time to see if we can get it to sit happily in the case

The final fiddly part of the process is to cut, size and trim a new stem, fit it securely to the crown, and insert into the movement, crown gasket freshly lubricated.  With that accomplished, fit the case back, flip it over and appraise:

The final touch as always, is the strap.  I gave this no thought at all because the only spare 20mm strap I had is a Phoenix military grey NATO which, as it turns out, suits the dark complexion of this one rather well:

and a wrist shot to finish

I reckon this is a pretty coherent result.  My wife does too.  So much so that she keeps ooing and aahing meaningfully.  But I’m not taking the hint.