I’m in the fortunate position that I get to see a great many watches cross my desk that the majority of people would have to attend private appointments in security filled boutiques to see. Yet, despite the vast quantity of watches I’ve seen, this is the first time a brand has sent some uncased movements for review, which presents a fascinating opportunity to get up close, break out the loupe and really get to know this calibre. And the movement in question is the Miyota 9075 Premium Automatic True GMT.
You’ll have noticed in our photography that there is a Miyota branded watch and as a quick explainer, it’s just a sample timepiece with a functioning 9075 movement equipped in order to see the movement in motion and explore its functions via the crown. This is not a watch review – it’s a movement review.
Let’s start with the size. It measures 4.92mm in thickness and a diameter of about 25mm excluding crown, which you can really appreciate when the movement isn’t in a case. It makes it a very versatile calibre capable of fitting in a wide variety of case designs and case sizes. For example, it powers both the 44mm Oceaneva Deep Marine Explorer VI 6000m and 37.5mm Héron Mirabel GMT Cigar Club. That slimness and versatility comes from the fact that it’s part of the Premium Automatic line, which is the moniker Miyota give to the ultra-thin series.
Turning the movement over reveals the oscillating rotor, which is famously one of the mechanisms that adds a lot of bulk to an automatic movement in comparison to a manual one. When being handled, you can feel the way that the weight is distributed right to the edge of the rotor, which is also where the thickness is, with the centre being very thin and lightweight. This configuration means the rotor is better at overcoming inertia to spin when you move your wrist and will continue to spin a bit when the movement comes to rest, improving its winding efficiency.
The other element that you can see really clearly is the balance wheel. A small golden ring with a spring at its centre. In order to see it in motion I have look to look at the exhibition caseback of the sample watch, where it oscillates back and forth like the heartbeat of the piece. It moves at a rate of 28,800 beats per hour (4 Hz). That’s the modern standard, providing a solid level of accuracy without the additional engineering required for a hi-beat, 5 Hz movement. Speaking of accuracy, it achieves -10/+30 seconds per day, which is perfectly adequate for a calibre this widely available and accessible.
Focussing in on the sample watch a bit more, it makes the functions of the calibre 9075 really obvious. It has four hands: hours, minutes, seconds and 24-hour. The seconds use a hacking mechanism, which means when you pull out the crown, the seconds hand stops, allowing you to set the time more precisely. The 24-hour hand is what makes this a GMT movement capable of displaying the time in two time zones simultaneously.
More importantly though, this is what is called a True GMT movement, as opposed to an Office GMT. What that means is that when the crown is in the first position, the main hour hand can be jumped forward and backwards in intervals of one hour (the date wheel can also be jumped forward and backward), so you can change your local time without having to reset the entire display. An Office GMT will move the 24-hour hand at the same time as the 12-hour hand and then you’ll have to re-adjust the 24-hour hand separately.
To round off the display is a date window at 3 o’clock. If you’ve seen a skeletonised date function then you’ll already be familiar with how this works, but it’s even more apparent on the non-case movement. It’s simply a ring the 31 days of the month that rotates once per day. It’s one of those things that makes sense logically but is not always intuitive.
It’s a fab little movement and while it was only introduced in 2021, it’s already a stalwart of the watch industry across accessible independent brands and microbrands. I’ve no doubt it will continue to be a dominant force in the True GMT department for years to come as well.
Price and Specs:
More details at Miyota.
