The most recent post on March, 17.2014 "Poor Man's Heuer Watches" showed me once again that some people are not aware how this industry works.
Maybe I can shed some light onto this with first hand experience. Watch making started in the 1800's and has evolved into a highly specialized industry over many years of up and downs. This is true before the Quartz invasion as well as for today, some players have changed but the production concept has remained the same. The point of this article is to make collectors aware of differences observed on collector time pieces and help them understand why and how these differences came about. This is pretty general but offers some explanations.
In the middle of the 1970's the Quartz "revolution" came about. People predicted the end of watch production as we knew it. The industry went into turmoil and thousands of watch industry workers lost their job. You can check the history elsewhere on who took control of whom, who stayed independent and which organization or companies eventually survived this shakeup.

This is not about history, but more about the many small companies that are the backbone of watch making, companies that supply the "Big Watch Companies" with specialized parts for all mechanical watches. These companies produce the Springs and Barrels, Hairsprings and Balances, Watch Cases, Crystals, Movement Plates and Bridges, Gears, Hairsprings, Dials, Hands-Pointers, Bezels, Seals and not to forget, Screws. All these parts require very highly specialized production methods and equipment / machines to produce these parts from raw materials to the specified end product. Then, the parts are shipped to small companies for initial subassembly work and eventually end up at the Major Brand Company. They collect all the parts and conduct the final assembly of their product. In other words, they DO NOT MAKE the parts for their watches, they ASSEMBLE watches. With the exception of a few companies, which have an in house development-test-laboratory-work shop, all these parts are made by other companies. It would be cost prohibitive to produce everything "IN HOUSE" instead they rely on those specialty subcontractors to produce the parts to the companies specification.
During the Quartz changeover and subsequent reorganization, many of these specialty companies were forced out of business and had to close shop. They had the knowledge and the equipment but no demand for their product. During this time many manufacturers and larger watch companies sold inventory to small companies which produced watches under their own logo. They could purchase parts at very reasonable cost because the mechanical watch future was uncertain. So we can see various collector watches from that time period looking just like the major brand watches. Ollech + Wajs for example, bought Breitling Parts when they closed shop and after assembly, sold Navytimer Chrono's under their own name labeled "Aviation". (Highly collectable now). There are many more examples like this. Jeff has shown pictures of some of them.
After the initial dust settled, a number of these companies re-organized, modernized and started production again since mechanical watches remained in demand after all. Today those companies supply the market again having made changes to adapt to the demands of the watch industry. This alone stands the reason why we can see subtle differences in watches and replacement parts.

People that quibble about authenticity should keep that in mind as well as the time frame when a part was produced. Maybe a subcontractor changed, or they made improvements or changes to their production method and the end product is slightly different. I have noticed a slight difference in patina / color on 2 new 11630 GMT Heuer bezels produced in 1974 and 1978. Both are Heuer originals, both authentic. Heuer and other companies have always made running changes during production. Authentic ?
you bet. Remember, they assemble watches, they fine adjust, overhaul/repair and service their products and have to use parts that were shipped to them. Is there a record of this? Only for the initial production line. For overhaul and repair, only in fragmented form of a service / repair invoice, if at all. So how are we to know exactly when certain changes took place or a new vendors parts were used. We don't. Variations will exist and there are no black and white answers. Only common sense, good judgement and the watches history could possibly help answer questions and help in it's evaluation. So the benefit of doubt should prevail before we critique a time piece too harshly.

You might ask how I know all this. I grew up in Switzerland and some of my friends and relatives are still active in this industry. But mostly, I gained first hand experience when we imported Dufeau Aviaton watches in early 2000 for about 5 years. I had access to the various companies that produced parts and assembled them into a finished product. My input and recommendations with respect to clarity, functionality, practicality and use of the watch as a pilots tool, were readily incorporated. We picked up watch cases from the stamping company in Saintlegier, checked on the assembly of the Valjoux/ETA movements in Grenchen, the mounting of dials and hands in Betlach and mounted wrist straps from Italy. Just to name a few.
These specialty companies are all scattered over western Switzerland. Small as well as large companies depend on these suppliers. Rolex, Omega, Heuer, Tissot, IWC and many others use the supplied parts and sub-assemblies to assemble their product and giving it the company's final touches. Once the watch goes to the dealer, the customer has further choices he can make to a specific model. This further complicates exact dating and verification of authenticity for a collector several years down the road.
The manufacturing process, time of production, overhauls, exposure to the elements, all should be considered when we evaluate one of these fine timepieces.
Remember there is no black and white and consider the watch industry's history also in the evaluation.

I would be interested in any feed back, comments, additions to the above since I believe that it addresses concerns by a variety of collectors. Thank you. Heinz Rengel.