The stamp that is found on the inside of many Fedoskino works, for example, is a stamp of the factory, not the village. Historically, the stamps of the Vishnyakov workshops separated their high-quality works from many of the other paper-mache producers of the 1800s. The use of stamps inside of boxes carried over into Fedoskino, where many of the Vishnyakov artists ended up.
Today, these stamps are placed inside the boxes painted by factory artisans which are then sold to lacquer art dealers through the factory artel. However, it is important to understand that while many dealers claim that the factory stamp is the only way to tell an authentic lacquer miniature, this is not always the case. The stamp (or lack thereof) can mean several things. Obviously cheap and mass-produced boxes that are sold primarily in the tourist centers of Moscow often carry the factory stamps, even though they are not painted or condoned by the factories themselves. (The same is true of some so-called certificates--many are simply mass-produced cards with no reference to the actual work, and can be included with a box arbitrarily).
Conversely, many of the more talented artists often work either partly or entirely freelance. Although working for the factory guarantees work for the artists, selling prices through the factory are much lower than the prices they can fetch by working directly with the dealers. There are trade-offs with either option, which is why many very talented artists stay at the factory exclusively, and many move on as quickly as possible. What this means is that works by some of the best artists of each of the villages will not always have a stamp on the inside.
In collecting lacquer art, it is important to view the quality of the box itself. Cheap imitations will naturally look cheap. A little decoupage box with a stamp is incomparable with a detailed piece by a master that is without the stamp. Next, find a reputable dealer. Sunbirds.com purchases its items either directly from the artists themselves, from the factories, or from a select few dealers in Moscow who are reputable, well-known, and who have special associations with artists and who purchase directly from them.
Don't be confused by the claim that a stamp is the only way to tell an authentic miniature--although it is an indicator, there are many other factors involved. As mentioned, the Fedoskino factory puts the "troika" stamp on the inside lid of the box. The history of the stamps can be traced in the book Fedoskino Lacquer Miniatures, from the early days of Vishnyakov, to the current Fedoskino trademark. Again, this stamp is only found in boxes painted by factory-employed artists. In the other villages, the situation is the same, only somewhat more complex. The implementation of stamps of these three villages are more recent, particularly those of Mstera and Palekh, where previously state-run enterprises have now turned private. In Palekh, there are several artels, each with their own artists and production facilities.