The Tudor Black Bay 58 18K is a stunning piece, but I understand your concern about the movement. While the MT5400 is slightly smaller and has a lower power reserve (around 70 hours compared to the 72 hours of the MT5602), it's still a COSC-certified chronometer and performs excellently in terms of precision and durability.

The main difference is the size, with the MT5400 being designed for slimmer cases like the BB58. It’s a solid movement for the watch’s dimensions and style. Although it might feel like a slight compromise compared to the MT5602, it’s not really inferior in quality—just different in size and use case.

If the aesthetics of the 18K model and the slim profile matter more to you, the MT5400 won’t disappoint in terms of reliability and performance.

 

I'm no Tudor expert. Very similar movements with same beat rate and approximate power reserve. I don't think you'll notice any real difference in the movement while wearing the watch.

 

OP, you have to remember that we are talking about tech that has been around for centuries and was eventually mostly perfected in the 1940's through the 1960's. But for a few recent never-been-done-before complications, nothing under the sun is really that new. What's new is that the latest couple of generations of watch buyers have been a bit more sophisticated and demanded better for the price-point, so we are in somewhat of a golden age for bang-for-the-buckness right now. Longer power reserves have been around for half a century, but there was no impetus to devise ways to make manufacturing them cost-effective. The ability to regulate a quality movement to better-than-COSC specs is similarly dated, but it isn't until recently that it became something buyers demanded. The point is, sure, the MT5602 is technically better than the MT5400 on paper. But in practical use? Both can be regulated to equally insane accuracy for an automatic watch. One gets you an extra 2 hours between power reserves that are equally overkill for somebody who wears a watch every day. The rest is hype. If you want the 18k, get the 18k. Don't worry about the movements.

 

All mechanical watches aren’t that accurate. Check your phone Time in Paris, France now - Time.is if you need more accuracy.

 

All mechanical watches aren’t that accurate. Check your phone Time in Paris, France now - Time.is if you need more accuracy.

For an automatic watch. Obviously, there is no mechanical watch on earth that will best an electronic device constantly updated against the atomic clock. Even Seiko's Springdrive is comparatively inaccurate to an iPhone.

With that point clarified, I think everybody can agree that we are definitely enjoying a golden age of accuracy and stability in mechanical watches right now. Longines makes a COSC high-beat 36'000 VPH diver that starts at $3,325. You can pick it up from reputable retailers for around $2,500. That's bananas.

 

I have serviced a MT5402 from a 2019 BB58.

My impression on the caliber is that its construction would be the equivalent to what Rolex engineers would produce if they were commisioned to design a caliber to outcompite ETA in the mass market.

With a fresh service, the caliber was EXCEPTIONAL with barely no delta between positions.

I can easily say this was the best performing caliber that has been in my bench. The silicon hairspring and the variable inertia balance - extremely good.

 

What do I think? Green is pretty but the 43mm blue bronze is more so!

My Tudor 79250BB - Preowned eBay $3000 and yup.

 

If you like the green and gold, but prefer the MT5602 caliber, there is also the Harrods edition:

 

If you like the green and gold, but prefer the MT5602 caliber, there is also the Harrods edition:

View attachment 18630235

I've come close to purchasing this many times. The dimensions kept me away after owning several bb41's and moving on from them.

I wish Harrods x Tudor would make this in a BB54 version, I think it would be an instant classic.

 

I would have confidence in either movement. It's a Tudor.