Tibetan silver in the modern sense is in reference to a silver alloy which contains copper, sometimes nickel or tin, and a tiny bit of silver. It is similar to pewter and is primarily used in jewelry components.
A decade or so ago, the silver content in Tibetan silver was up to 30% or higher, but today it is extremely low due to deliberate dilution. “Its overall appearance is of aged silver, but it can be polished to provide highlights on complex castings. The nickel content is nowadays reduced or absent, due to common allergies to this metal. Currently, jewellery, beads and castings described as ‘Tibetan Silver’ tends to be a base iron ‘cheese metal’ casting, overlaid with this pewter and silver plating. Dependent on source, these can be either thick and robust, or attractive but easily broken due to a loose, fragile inner casting. The latter productions are therefore only suitable for small castings up to around 12mm, or transient ‘fashion’ jewellery with a short lifespan” (Wikipedia).
“Metallurgical testing of twelve items in 2007 offered for sale on eBay as Tibetan Silver indicated that the articles frequently contained no silver whatsoever. Tests also found that high levels of lead and other dangerous metals such as arsenic were present” (Wikipedia).