Do you know if it is possible to have a CW watch that have c63 sealander 36mm case and sellita cosc movement (like c65 sandhurst) ???

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Movements are as listed in the CW Forum Archive. They wouldn’t put a different movement into a single watch.

Two options would be...
1. Swap out the movement for a COSC version.
2. Regulate the movement to as close as possible to COSC specs.

Personally, if I were looking to swap movements, I'd upgrade to the JLP G100, if you can find one.

As above, CW won’t do the work to swap a movement on an individual watch, but as the existing Sellita in the watch is a common movement you could swap it yourself or have a local jeweler do it for you. Regulating the existing movement would be less expensive a route and unless you’re experienced to do it on your own it’s a job a jeweler can perform. It’s a benefit of using a standard movement that’s already pretty good. You’ll void the CW warranty, however.

I believe that CW would be willing to swap a movement on an individual watch if the customer is willing to pay for the service. I also believe that CW has the expertise to perform this type of work.

@virgilmerk Have you asked them?

I recently asked CW if I could get a COSC in a C65 Aquitaine and the reply was, "No, sorry."

virgilmerk wrote: ↑Mon Nov 20, 2023 8:39 pm I believe that CW would be willing to swap a movement on an individual watch if the customer is willing to pay for the service. I also believe that CW has the expertise to perform this type of work.

Ohh, then sorry to confuse you(

luke31 wrote: ↑Sun Nov 19, 2023 10:17 am Do you know if it is possible to have a CW watch that have c63 sealander 36mm case and sellita cosc movement (like c65 sandhurst) ???

I have a 36mm Sealander with standard SW200-1 which is working within COSC specs at -2 sec/day. I also have an ORIS Hunter Team PS with Sellita SW200-1 cal which is at +2.3s/day. You can regulate it yourself with a rubber ball borrowed from your dog (wash the slobber off first) a 1mm screwdriver, +5 loupe and a steady hand. Why go to the expense of replacing the movement with a COSC which could still be out by up to ±4s?

NigelS wrote:Why go to the expense of replacing the movement with a COSC which could still be out by up to ±4s?

Because COSC movements are always of a Top spec, so have better components than regular movements, making them more likely to run well for longer in the future.

The COSC movements seem like the way to go in my estimation (to each his own); however, being able to tweak a movement yourself (which I only just learned about from this forum) is an awesome opportunity to get the most out of the standard movement in those cases where the COSC is not an option, like the C65 Aquitaine that I'm eyeballing.

welshlad wrote: ↑Tue Nov 21, 2023 2:08 pm

NigelS wrote:Why go to the expense of replacing the movement with a COSC which could still be out by up to ±4s?

Because COSC movements are always of a Top spec, so have better components than regular movements, making them more likely to run well for longer in the future.

welshlad wrote: ↑Tue Nov 21, 2023 2:08 pm

NigelS wrote:Why go to the expense of replacing the movement with a COSC which could still be out by up to ±4s?

Because COSC movements are always of a Top spec, so have better components than regular movements, making them more likely to run well for longer in the future.

Indeed so, but is it really worth the extra cost of replacing a std movement with a top spec COSC especially as they'll both need servicing in the future anyway?

^^^ Well, I certainly wouldn't see the value in doing it, especially if the watch is still in warranty. If the watch was out of warranty and the existing movement had proven to be seriously problematic, then I could conceivably consider it, but that would be a rare circumstance.

NigelS wrote: ↑Tue Nov 21, 2023 4:31 pm

welshlad wrote: ↑Tue Nov 21, 2023 2:08 pm

NigelS wrote:Why go to the expense of replacing the movement with a COSC which could still be out by up to ±4s?

Because COSC movements are always of a Top spec, so have better components than regular movements, making them more likely to run well for longer in the future.

Indeed so, but is it really worth the extra cost of replacing a std movement with a top spec COSC especially as they'll both need servicing in the future anyway?

It isn't only about servicing. The upgraded parts in the COSC/TOP grade movements are more stable across temperature and have a finer tolerance to variation. This equates to a movement that will drift far less over time and temperature. There is a reason that the specs are wider for the Elaboré and Standard grade movements. It isn't just because they aren't regulated well.

At service time it wouldn't bee too much more to have the watchmaker bin the movement and replace it with a top grade or COSC. (note that the top grade is the same components as the COSC just not tested thus lowering the cost a bit).

rkovars wrote: ↑Tue Nov 21, 2023 10:51 pm

NigelS wrote: ↑Tue Nov 21, 2023 4:31 pm

welshlad wrote: ↑Tue Nov 21, 2023 2:08 pm Because COSC movements are always of a Top spec, so have better components than regular movements, making them more likely to run well for longer in the future.

Indeed so, but is it really worth the extra cost of replacing a std movement with a top spec COSC especially as they'll both need servicing in the future anyway?

It isn't only about servicing. The upgraded parts in the COSC/TOP grade movements are more stable across temperature and have a finer tolerance to variation. This equates to a movement that will drift far less over time and temperature. There is a reason that the specs are wider for the Elaboré and Standard grade movements. It isn't just because they aren't regulated well.
At service time it wouldn't bee too much more to have the watchmaker bin the movement and replace it with a top grade or COSC. (note that the top grade is the same components as the COSC just not tested thus lowering the cost a bit).

I completely understand and agree, except the point I'm making (perhaps not very cogently) is that the Sealander 36mm is an inexpensive watch but the movement that can be regulated to achieve better accuracy than that with which it comes out of the factory! I also understand the OP likes the watch but requires a top grade calibre which CW doesn't offer for this model - incidentally there are makers out there like STOWA who do give a choice of calibre with a 36mm case. My response to @luke31 was to try to help him save some money and still achieve a tolerably accurate piece by regulating the standard movement himself.

PS Happy Birthday to yourself!