The company's name is Jenavi, they have been based in Saint Petersburg, Russia since 1991. They were formerly named as ETALON-JENAVI until 2011 when they rebranded to just JENAVI.
I'm not sure what to make of the marks or the metal content. They state:
A hypoallergenic galvanic covering with precious metals (24 karat gold, 999.9 standard silver, rhodium) is used for the jewelry production.