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Calibre 8500: Do they all have a silicon balance spring?

Archer
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EuroDriver EuroDriver
I don't think that the silicon balance spring in and of itself will bring an 8500A to "Master Co-Axial" spec. The 8500G had additional parts updated with non-magnetic parts (although I couldn't find out exactly what those additional parts are) and the upgrade would still lack the official Master" certification, just like the 8500B.

Additional parts are the pallet fork, co-axial wheel, balance staff, and shock springs on the cap jewels...going from memory...
 
josiahg52
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Yeah, I think that pretty much sums it all up. I'm interested in a blue teak Aqua Terra. Not sure which one, though. I think the cal. 2500 watches are nice, too. I like the cal. 8800 in my new Seamaster and the accuracy potential it brings. The Skyfall Aqua Terra is a neat piece. I was just getting confused with what each version bought to the table. This helps very much.
 
EuroDriver
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I expanded my previous reply to your earlier observations to clarify in more detail. Good luck on your search and let us know which one you acquire.
 
josiahg52
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EuroDriver EuroDriver
I expanded my previous reply to your earlier observations to clarify in more detail. Good luck on your search and let us know which one you acquire.

Really, very helpful. Cleared up much of my confusion.
 
JDB6Nine
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Hello, The AT with 8500 you are seeking does have Si14. However, not all 8500s have the Si14. When the 8500 was originally launched in 2007 in the DeVille Hour Vision, it had a Nivarox hairspring. The Si14 was released in 2008, so 8500s have it thereafter.
 
EuroDriver
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Thank you for the info.
Through my research, I found out that the AT "Skyfall" were among the first - if not the first 8500s to receive the Si14 balance spring.

I finally got my 41.5mm Skyfall and I can confirm it has the Si14 hairspring
 
502 to right
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Two years on and I'm still loving my Skyfall Aqua Terra and it has become my daily wear watch. I sold the Master Co-Axial version.

My Skyfall had just been serviced by OSC when I bought it and it's my best running watch. Consistently +1 second per day. I love the blue dial, especially in the sunshine. And it's so versatile. It looks good with shorts and a T-shirt or a dinner jacket.

I also own a 2541.80 GoldenEye that has just been sent off to OSC for an overhaul. I prefer my dive watch to be quartz since I primarily wear the AT. That way when I pick up the diver I don't have to fuss about with setting the time.

Bond 5.webp
 
EuroDriver
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My Skyfall is currently out for service. It will be interesting to see what parts get changed.
 
502 to right
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EuroDriver EuroDriver
My Skyfall is currently out for service. It will be interesting to see what parts get changed.

Was there a problem?
 
EuroDriver
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502 to right 502 to right
Was there a problem?
It was in need of a little TLC. Particularly, a lot of small scratches on the AR coating. I took it in primarily to replace the crystal but while at the OB, they encouraged me to have it tested and although it was running fine, the amplitude results were a little low.

Service was not necessary at this point, but I decided to have it done since I was sending it in anyway because the crystal was really bugging me.
 
S
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EuroDriver EuroDriver
Yes, but no: There was an in-beteeen.

The first cal. 8500 (known as 8500A) did not contain the silicon balance spring. It is designated "Co-Axial."

Shortly after, the 8500B was quietly released; it contained the Si14 balance spring but kept the Co-Axial designation. It seems like it was released along with the blue dial "Skyfall." Specs state it resists magnetic fields up to 15,000 gauss but it is not COSC certified.

Finally, the 8500G was released. It contained the Si14 balance spring and additional Si14 components. It was designated "Master Co-Axial" and is COSC certified to resist magnetic fields to at least 15,000 gauss. Rumor has it that it received the designation of "G" instead of "C" to represent its certified gauss rating.


The 8500A does not have a silicon balance spring. The 8500B does, but is not Master certified.

I don't think that the silicon balance spring in and of itself will bring an 8500A to "Master Co-Axial" spec. The 8500G had additional parts updated with non-magnetic parts (although I couldn't find out exactly what those additional parts are) and the upgrade would still lack the official Master" certification, just like the 8500B.

I'd still take the silicon balance spring over the older one regardless.
Wrong. The Cal.8500A has a metal balance spring and no real resistance to magnetic fields it was introduced in the Hour Vision in 2007 and was then used in the Gen2 Aqua Terra in 2008 and the Constellation ‘09 in, you guessed it, 2009. This movement continued until 2011. It was then replaced with the Cal.8500B which has silicon (Si14) hairspring. It has increased resistance to magnetic fields, around 300 Gauss to 500 Gauss. Both the Cal.8500A and B are Co-axial chronometers, COSC certified. Neither can resist a magnetic field of 15000 Gauss.

The next development was the Cal.8508 used in the Aqua Terra >15000 Gauss in 2013. This is still a COSC certified Co-axial chronometer and can resist magnetic fields of at least 15000 Gauss. This is a movement only ever used in the Aqua Terra >15000 Gauss.

In 2014 the Cal.8500G was introduced which was a “non-special” version of the Cal.8508, basically it did not have “Cal.8508” and “>15000 Gauss” engravings. It was still a COSC certified Co-axial chronometer. It only ever appeared in the Gen2 Aqua Terra 38.5mm and 41.5mm time and date only watches. No other Gen2 Aqua Terra has a movement that resists magnetic fields of at least 15000 Gauss. The only difference to the earlier Gen2 Aqua Terra watches is the deletion of the date window surround and a hand set that is the correct length for the 41.5mm case. These watches are termed “Master Co-axial”. This is because the silicon hair spring is not the component that guarantees the magnetic field resistance but rather a whole suite of modifications to the components and the materials they are made out of.

To reiterate the Aqua Terra Day-Date, Annual Calendar and Chronographs do not have movements that resist at least 15000 Gauss and nor do the Planet Ocean, De Ville Co-axial, Constellation or Hour Vision watches equipped with the Cal.8500 as by 2011 they had all been upgraded to the Cal.8500B (Si14 balance spring).

The only other watch with a COSC Si14 Cal.8xxx “Master Co-axial” movement is the Seamaster 300 from 2014 with the Cal.8400G.

In 2015 Omega introduced the Cal.8900 COSC and METAS certified “Master Chronometer” movement that has a modified gear train and the METAS certification and can resist at least 15000 Gauss.
Edited:
 
S
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EuroDriver EuroDriver
Thanks. The reason I asked is because I saw a YouTube review of the AT 8500 which said it had shorter hands than the newer "Master Co-Axial." However they youtuber stated that the blue dial "Skyfall" had the longer hands but he was not able to confirm it.
The 41.5mm Gen2 Aqua Terra time and date watches with, black, grey and silver dials with date window surrounds all use the had set from the 38.5mm watch so the hands are too short to reach the seconds/minute markers or the hour markers. The same 38.5mm hand set is also used on the first version of the Aqua Terra Annual Calendar 43mm (the one with the “coffin” shaped month and date window surround) and the GMT 43mm (non-chronograph). Obviously on those larger models the short hands are far more noticeable than on the 41.5mm. It makes using the GMT in low light conditions virtually impossible because the minute, seconds and GMT hands are virtually identical in length and all have arrow shaped lume plots on the tips. The blue dial 41.5mm Aqua Terra time and date with the date window surround is the only version of that Aqua Terra that has the correct length hands for its dial. All subsequent Aqua Terra watches except the GMT were supplied with the correct length handsets from the Day-Date 41.5mm in 2013 onwards.
Edited:
 
S
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josiahg52 josiahg52
The first cal. 8500 movements didn't have a silicon spring but were co-axial movements.

Later, they became Master Co-axial movements with the change to a silicon spring.

The silicon spring can be fitted to a cal. 8500 bringing it to the Master Co-axial "spec". There was likely overlap so some Master Co-axial watches may not be labeled as such. This means the lack of the word" Master" doesn't mean a watch doesn't have a silicon spring from the factory and especially as a result of a service.

Then, the cal. 8900 came about which is the METAS Master Chronometer movement with a silicon spring and is still a co-axial movement.

The 8500 and 8900 have a quick-set hour hand. The date is changed by rotating the hour hand through 24 hours, I assume.

The 8900 moved the date to 6 o'Clock.

I'm not challenging what's been posted above. I'm trying to put it in my own words so I understand. Please correct me if necessary.
You are wrong. See my reply to euro driver above for a brief rundown on the development of the Cal.8500 movement. The use of a silicon balance spring does not give magnetic field resistance to at least 15000 Gauss. The Cal.8508 was the movement that introduced that level of magnetic field resistance and it is carefully explained by Omega how this is achieved by using non-ferrous materials and new compounds to make the movement. Fitting a silicon balance does nothing to achieve your so-called “Master co-axial spec” nor would a service ever do this as it would require the replacement of the entire Cal.8500A or 8500B movement with a Cal.8500G. A Cal.8500G is also not interchangeable with a Cal.8900 as it is not as is often claimed a “relabelled” Cal.8500G. It has a number of components that are reshaped and or replaced to maximise efficiency. The Cal.8900 also has different lubricant requirements compared to the 8500G as well.
 
EuroDriver
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On page 2, I included a link that explains the evolution of the Calibre 8500 movement. I'll re-post the link to the article: http://watchcharts.com/articles/p/1...500a-8500b-8500g-8800-8900-co-axial-movements

Based on the comments shared by @Spqr
I did some additional research and to expand on some of my earlier posts, I want to emphasize that I misunderstood earlier statements regarding the upgrading of the 8500b at service. It is actually the 8500a that will be upgraded with a Si14 balance spring at service.

Here's another article giving a more thorough explanation: https://watchcharts.com/articles/p/...500a-8500b-8500g-8800-8900-co-axial-movements
Edited:
 
Vinz Clortho
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Did someone say Bumblebee? Funny thing was read the article on the forum a while back and always said "If I was going to add an AT, that would be the one." Right before Xmas this year, had the chance and wasn't going to pass on it.

The yellow and black second hand plays well against the vertical teak pattern and yellow accent color.

20250209_025115.webp
 
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