Sometimes the center is the capital of the nation that contains the tribes or at least a part of several tribes. Tribes do not fit neatly into boundaries. Think of the native Americans in Alaska or Canada and the Pacific Northwest. That is the picture in Central Asia.
However, the urban center usually has the greater advantage when the artisan wishes to produce a product with an organic unity, such as an important piece of jewelry. I have posted several times on the symbols and their meanings expressed in silver and gilded silver jewelry among the Turkoman tribes. Here is an expression of their reverence for a mountain symbol:
Probably produced from an urban tribal silversmith.
More detailed information on this piece at http://www.artfire.com/ext/shop/product_view/craftsofthepast/4053403/Antique
The reason I would guess that the piece in the photo above came from an urban silversmith is that it puts to full use the specialties required to yield a unified expression in silver of the Turkoman mindset regarding the ancestral mountain, the source of the Turkoman people. First, let me say that this is only half of what the silversmith created as the full expression. This is one of the hair pieces that a woman wears pinned into her braid or her veil at a point just above each ear. Such pieces are created in pairs. I have the piece that matches this one.
The Turkoman people like replication. Not only of the symbolic jewelry pieces themselves, so often produced in pairs, but of the motifs carried out inside the exterior expression. See all the smaller mountain shapes made of silver grains dropped patiently and uniformly again and again expressing the ancestral pyramid shape. What would you guess the opposite side of this piece looks like? Surprise! it looks just like this side. They are two identical pieces except for the stones in the small rosette, joined to make a hollow silver hair or veil ornament that respects the source of the tribe.
The pendant in the photo below is a rural piece from Afghanistan (one of the nations that contains a part of a few of the Turkoman tribes). This pendant reveals its rural craftsmanship in its lack of a specialist to inscribe the water and floral symbols in the center of the plaque. That part of the piece is amateurish, while the rest of the piece is made at a higher skill level.
You can see more detailed information on this piece at http://www.artfire.com/ext/shop/product_view/craftsofthepast/4056415/