A ".925" or "sterling" stamp means the piece is sterling silver — an alloy of 92.5% pure silver and 7.5% other metals, usually copper. The small amount of added metal makes the silver hard enough to wear, while the 92.5% standard guarantees a high silver content. It is a metal mark, separate from the artist's hallmark.
Pure silver — "fine silver," .999 — is too soft for most jewelry; it bends and scratches easily. Alloying it with a little copper produces sterling silver, which keeps silver's bright luster but gains the strength a wearable piece needs. The ".925" figure is simply the silver content expressed as a decimal: 925 parts per thousand.
On Native American jewelry you'll usually find the sterling mark stamped on the back — inside a ring band or bracelet, or on the reverse of a pendant. It tells you about the metal only. It does not identify who made the piece; that is the job of the separate maker's hallmark, which may be the artist's initials, a pictorial symbol, or a clan emblem.
You may also encounter "coin" stamped on older pieces. Before sterling stock was widely available, some Southwestern silversmiths worked from melted coin silver, which has a slightly lower silver content than sterling.
Be careful not to confuse a sterling mark with terms like "silver plate," "nickel silver," or "German silver." Those are not sterling at all — plated pieces have only a thin silver layer over a base metal, and "nickel" or "German" silver typically contains no silver. Genuine sterling has real weight and a warm shine that those substitutes lack.
When you're evaluating a piece, look for both marks together: a metal mark ("sterling" or ".925") confirming the material, and a maker's hallmark identifying the artist. The two together are a strong foundation for authenticity — best confirmed by a Certificate of Authenticity.