925 is a standard sign used to mark sterling silver, and the meaning of the stamp is that the silver content in the piece is 92.5% (i.e., the remaining 7.5% is comprised of other elements).
If you see the number 925 stamped on gold jewelry, chances are that the mark does not refer to the gold content of the piece.
This is not so surprising, however, and most likely means that the jewelry is not made of solid gold but is actually a silver piece that has been gold plated.
A “925” mark is usually stamped on gold vermeil. So, if your gold piece is marked with a “925” stamp, what you have is likely gold vermeil (pronounced ver-may). This is the name used to denote silver jewelry covered with a thin layer of gold.
For more info, see JewelryNotes.com - What Does a “925” Mark Mean When Stamped on Gold Jewelry?.
Tips! Learn seven ways to tell if your gold is real at MoneyMorning.com.
Of interest, find out the most expensive jewelry in the world, compiled by The Richest.