The MST 436/470 (437/471 with date) was a prestige movement family designed and produced by Roamer in from 1964 in a no expense spared effort to move the brand upmarket. It worked too, because the movement was innovative, robust and long lived. It featured in the top of the line Mustangs and Stingrays for almost a decade. With 44 jewels, the best versions of these movements have the most jewels (that I know of) that are really functional.
While not all 44 jewels are absolutely critical for good timekeeping, and some English old timers back in the 1800s would have argued that 7 jewels in a lever escapement are all that are needed, the added jewels do add to the longevity of the precision of a movement – that is, the length of time it will continue to work within design parameters. Lets look at where all these jewels live in the movement.
The first 7 jewels on any lever movement made with a modicum of of pride are:
Balance, olive and cap jewels on the balance staff = 4.
Impulse jewel = 1
Pallet jewels, to engage the escape wheel = 2
Total = 7
Before World War II, 15 jewel watches were considered fully jeweled (hey I am not talking about railroad watches here!) and these were in the wheel train.
Pallet/lever/anchor arbor = 2
Escape wheel = 2
4th wheel = 2
3rd wheel = 2
Total = 15 (7 + 8 )
The around about WWII people decided that 15 jewels weren’t enough and a fully jeweled manual wind watch would have 17 jewels.
Centre wheel = 2
Total = 17 (15 + 2)
So where in the 436/470 are the extra jewels, over and above the 17 jewels we have all come to love?
First things first, Roamer used a 5 wheel train, incorporating the centre seconds wheel into a 2 layered train. So that is 2 more jewels = 2
Movement Total = 19 (17 + 2)
Next, Roamer fully jeweled the automatic winding ‘train’, which is 2 coupling clutches, plus 2 more wheels – so 4 x 2 = 8.
Total = 19 + 8 = 27
In the 44 jewel version of the movement, the coupling clutches I previously mentioned have, a total of 10 (5 each) ruby ball bearings, running between beryllium and steel plates. While steel balls as in the 28 jewel version also work, the ruby balls are essentially frictionless and non wearing. In the 44 jewel versions this a non-wearing part that will last indefinitely when treated (by the watchmakers) appropriately (i.e. don’t put them in your cleaning machine) so, 2 x 5 = 10
Total = 27 + 10 = 37.
And the last 7 jewels, they are sitting in the rotor bearing. Which, as it turns out, was better for advertising than longevity – as impact damage can cause the ruby rotor bearings to fracture. Many of the 44 jeweled versions now live with 37 jewels, with the ruby bearing unit replaced with a steel ball bearing unit from the lesser models of the family. The ruby bearing units are no longer available and were swapped out in service during the 1970s.
Total = 37 + 7 = 44
And there you have it. Each and every one of the ruby jewels performs a functional role in the movement, and besides – all those jewels make the movement look great and assemble easily. I am not entirely certain which jewels are where in the 28 jewel version, as the obvious count is 27 – I will look into this later.