Hi Colleen, in Russia the state-controlled hallmarking of jewelry articles was enacted in 1613, for silver items, in 1700 and for gold items, while in the USSR in 1927 this was done for platinum items and in 1956 for palladium items.
The Madonna and child in jewelry art history is an entire subject in itself. The jewelry representations of Madonna (My Lady) and child are central icons of Roman Catholicism and Eastern Orthodox Christianity and that is why Madonna and Child Pendants were made by master workers in Italy and Russia. The star indicates a Russian touch-mark, however without the benefit of a photograph there is little else I can add.