I'm not an expert, but I'm under the impression that most Navajo and Hopi jewelry was coin silver. Now that silver coins have dried up they must have to purchase silver, but again, I've never heard of Navajo or Hopi made jewelry having a content mark like 925, which is sterling. I've also been told that the 925 indicates it was made in Mexico, which is their mark for sterling. I guess other countries use 925 also, but the US mark is sterling.