Sorry to read you think it is because it is not. I just asked Omega questions about the Speedmaster Calibre 321, and noted down their answers. Do you also feel the two-fold assembly at Lange doesn't make any sense? Or just in this case? When Omega explained it, it sounded quite interesting tbh. When you disassemble the parts, I can imagine you can see (based on signs of wear?) if all components work flawlessly together. Make adjustments, and assemble it again. Correct me if I am wrong.
I don't know why ALS claims to require this double assembly, so I can't comment regarding the validity of their reasoning. The watch factories that I have been in where double assembly is required are only for very intricate and complex movements that are highly decorated. After the initial fitting is done, the movement is taken apart and further finishing/decorating steps are taken (often by hand), before the final assembly. This is done to ensure that resources required to hand finish parts are not taken up by parts that might not be suitable as finished parts, or where a further adjustment would possibly damage the hand finishing. The one that jumps to my mind right off is the JLC Gyrotourbillon - assembly done in the farmhouse - I suspect you have likely been there also...
You can see that various aspects of this movement are not yet fully finished.
In a service situation, when I am servicing a watch of any kind, the watch is disassembled, cleaned, and then parts are checked for wear - typically done under the microscope:
When wear is evident, a decision is made on how to proceed - repair or replace. This will be dictated by the degree of wear, plus the availability and price of the part in question. This doesn't require assembling the movement to find out.
As I said, sometimes you will get a part that isn't correct, right out of the package - here's an example of a wheel that has no pinion leaves machined into it:
Beside a replacement that is at it should be:
More common is a bent wheel, so what I do (as do most watchmakers) is that when you are say assembling the wheel train, when you get the bridge on you turn the stem and get the wheel train turning, and watch for wobbly wheels. This is done before lubrication (at least that's how I was taught) and if you see a bent wheel, you remove the bridge and either fix the bend, or in the case of a factory setting, get another one out of the drawer, put it in, and move on.
Now certainly there is the odd time when you get the watch ticking, and find that something is amiss, and it requires you to take the movement apart again, find the problem, clean everything again, and assemble it again. But this is rare - rare because it takes time to do this and time is money. As I often have advised people who are learning, when servicing a chronograph watch I assemble the base movement first - enough parts to make the movement run, but no more. I then do all the timing checks and adjustments, because if I find that there's a problem that requires disassembly (low amplitude, wobbly timing results, etc.), I don't want to have to take all the unrelated chronograph parts off the movement. I only put those on once I know the base movement is fine.
If Omega is saying that this double assembly is done on every movement, it's baffling why that would be needed on a bog standard chronograph movement using massed produced parts. It smells like pure marketing to me, unless some additional details could be added to explain why this is needed.
Cheers, Al
