A manufacture is a watch factory that designs develops and manufactures, at least, one complete caliber “in-house.” This has been the definition of the term for as long as I can remember. Anyone who tells you otherwise is wrong.
The use of the word “manufacture” or “in-house” initially came into popularity as a marketing term used to differentiate timepieces which have exclusively designed, developed and manufactured calibers, versus those that don’t. On the surface, it is a very simple distinction. However, due to improper use of the term, primarily by watch companies and journalists, the definition has become muddled.
With such ambiguous use, the term has evolved to the point where there are essentially different levels of in-house movements: true in-house or primarily built in house. Instead of getting too in-depth into the different levels, I will just say that certain watch movements, qualify or not, based on an inexact set of criteria. This may decrease the impact of the term somewhat, but it should not negate the importance of what it means.
Ultimately, an in-house movement is designed, developed and manufactured, primarily in the respective manufacturer. Some parts, such as the hairspring (one of the most difficult watch components to manufacture), may be sourced outside the manufacturer, which is common and does not take away from the fact that a high percentage of all the work to make the caliber a reality – have been manufactured within the factory.
Rolex and Grand Seiko make every component of their movements, and even the entire watch, in-house – and that is awesome. They are “true manufactures” – meaning they are 100% vertically integrated. However, there are still plenty of companies (that we won’t name here) that are considered manufactures, even if they do not integrate every single process to create their movements in-house.
On the other end, there are many companies who mislead consumers, by using exclusively made movements, that were designed and mostly manufactured outside of their factory, and those, while exclusive to their company, are not manufacture movements. And even worse, some companies will even market a 100% outsourced movement as a manufacture caliber with not even making a single upgrade or modification.
Bringing even part of the manufacturing operations inside versus outsourcing is generally considered a good thing. Having said that, there is nothing wrong with a watch company buying some or all of the components for a watch movement outside of the company. The problems happen when a company is not accurate in the marketing of the product. Or when they overcharge for a base caliber (such as an ETA or Sellita) without adding any value to the actual movement, such as additional finishing, new components, new modules, and so on.
In summary, yes the terms “in-house” or “manufacture” are imprecise, but that does not mean they are irrelevant.
The fact of the matter is that these terms, when used correctly – generally distinguish a caliber with a unique design, finishing and so on. Don’t be mislead, the label “manufacture” movement does matter.