In our opinion these items are probably of Russian origin and are typical jewels of the time in their closed back silver setting.
Survivors from the 18th century
A very rare pair of diamond jewels dating from the mid 18th century
This type of close pavé setting inspired the fashion for micro-pavé setting which enjoyed great popularity in the closing decade of the 20th century and are still fashionable today.
It is clear that the diamonds have been chosen for their size and shape and were not cut to fit the mount; a century later, when diamonds were already much more plentiful, a much wider range of stones would have been available to the jeweller to choose from.
The elements composing these two jewels are not connected by means of silver links but are strung together on wire like beads. As is clear in the photograph of the reverse of the necklace, each of the links is numbered suggesting that the jewels could have been disassembled.