Vintage Movement Accuracy

[AllBusiness]

A very broad question, to be sure, but how accurate were vintage Rolex movements? I’m not asking about a specific caliber, but just generally. Today, Rolex movements are certified to –2/+2 seconds per day, but what tolerances would we have seen, for example, in the 1960s and ‘70s?

[StanGMT]

As I understand it, COSC certification has always required +/- 2 sec/day. My 1967 1675 GMT was COSC certified when new and still keeps within the +/- 2 sec tolerance.

Stan.

[Dan S]

Originally Posted by StanGMT

As I understand it, COSC certification has always required +/- 2 sec/day. My 1967 1675 GMT was COSC certified when new and still keeps within the +/- 2 sec tolerance.

Stan.

-4/+6 average daily rate, IIRC.

[Old Expat Beast]

Unfortunately this letter is undated, but I believe it's from the late 1960s. Anyway, whenever it was written, Chronometer specs were -3/+13 spd and Rolex tightened that up to a "superlative" -1/+10.

I cropped this letter from a TRF sales listing several months ago as I found it interesting, but I forget whose it was. I apologise for that and if the seller would drop me a PM I'll give him full credit for this pic below.

[Tools]

COSC did not exist until 1974 when the Swiss Industry decided to standardize their Chronometer Certification. Those standards are the same today as they were then, a 10 second swing (-4 to +6 from test start) during torture testing.

Rolex, prior to that, were considered 10 second movements daily, although the often performed better.
Faster Beat movements could usually run at 5 seconds per day.

Today Rolex advertises that their watches are timed for 2 seconds daily, and most of them can do that. This is pretty cutting edge for a mechanical movement.

[AllBusiness]

Thanks, all. I appreciate the answers. Good to know that Rolex movements have always been quite accurate.

[Old Expat Beast]

Originally Posted by AllBusiness

Thanks, all. I appreciate the answers. Good to know that Rolex movements have always been quite accurate.

Not all Rolex movements were chronometer rated. Well into the the 21st century, Air-Kings, for example (up to ref 14000m), were not. They were accurate, but not chronometers, hence the word "Precision" on the dial.

[Model12]

Originally Posted by Old Expat Beast

Not all Rolex movements were chronometer rated. Well into the the 21st century, Air-Kings, for example (up to ref 14000m), were not. They were accurate, but not chronometers, hence the word "Precision" on the dial.

On a related note, I put on my 14000M eleven days ago, and I am 2 seconds slow. Daily wear, face up at night.

My watchmaker DID adjust it twice for me to get this level of accuracy.

[brandrea]

Originally Posted by Old Expat Beast

Unfortunately this letter is undated, but I believe it's from the late 1960s. Anyway, whenever it was written, Chronometer specs were -3/+13 spd and Rolex tightened that up to a "superlative" -1/+10.

I cropped this letter from a TRF sales listing several months ago as I found it interesting, but I forget whose it was. I apologise for that and if the seller would drop me a PM I'll give him full credit for this pic below.

Thank you for sharing this Adam, great stuff

[007Sub]

Vintage movements can be quite accurate. But a lot of it depends on the type of movement/balance (ie. 1520 vs 1570) and the extend to which watchmakers prioritize things like poising and hairspring adjustment during service intervals.


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[Eric88]

Not sure if I've detected a trend, as my sample size is small (5 or 6 different vintage Subs). I have found that vintage, recently serviced, tends to run just a bit fast in a good way, such as .5 seconds a day or less. I'd rather have it running a little fast than a little bit slow. My modern Sub tends to run just a little bit slow.

[WilsonCQB1911]

I recently got my 1675 serviced by Rolex. I also have a current reference no date Sub so I can provide some comparison. The modern Rolex is more precise. By that I mean that regardless of what position it is it runs at essentially the same speed.

My Sub is a solid -2 spd watch if literally worn 24/7 (to bed as well). If I wear it all day it is a -1 spd watch and then it regains that second while it rests at night. That's how I run it now and I wear something different at night. So the Sub is always at the exact same time in the morning.

My GMT has much more positional variance but is still well within COSC. That watch if worn 24/7 is actually a 0spd watch but if I rest it at all I find it'll start gaining a few seconds here or there. Regardless, it is still an incredibly accurate watch and better in terms of accuracy and precision than many modern watches by other brands.

[padi56]

Originally Posted by AllBusiness

A very broad question, to be sure, but how accurate were vintage Rolex movements? I’m not asking about a specific caliber, but just generally. Today, Rolex movements are certified to –2/+2 seconds per day, but what tolerances would we have seen, for example, in the 1960s and ‘70s?

No the modern day Rolex movements are first tested at the Swiss COSC to a average of -4+6 seconds to get chronometer certification.Then Rolex further checks on a machine to this new precision -2+2 seconds test if pass at time of testing,but on the wrist wearing could vary..But for any purely mechanical watch to run within a few seconds out of 86400 seconds in a day truly is a mechanical marvel.