Are you sure it is fspo? ESPO is the name of a vintage jewelry company. I see it on many gold filled rings.
In the periodic table AU stands for Gold, otherwise known as Aurum.
It may mean that the ring is made of sterling silver.
What does MNSN On sterling jewelry mean
Probably means that it is sterling silver.
The sterling silver standard has a minimum millesimal fineness of 925
It is an abbreviation of the word "sterling," meaning that the piece of jewelery is made from sterling silver.
It means that 99.8% of the mass is silver. Sterling has a minimum of 92.5%.
Not Really
Means it is Sterling Silver
yes
Nickel Free 925 silver. Namely, sterling silver which is free of nickel traces.
927 is sterling silver