The company in Leningrad was founded in August 1936, when SOYUZYUVELIRTORG was created, uniting a number interregional offices and departments for the wholesale and retail trade in jewelry. I think that was the earliest ЮВЕЛИРТОРГ, followed by compasnies of the same name in other towns.
As explained above, ЮВЕЛИРТОРГ existed in many Soviet regions, as late as mid 20th century (see the page of their book in another town dated 1957).
The quality and Art Nouveau decor of your cigarette case, in my humble opinion, indicates very early production, i.e. twenties of 20th century. The quality deteriorated significantly when compared with Imperial silver, although a comment is needed in regard of new Soviet state after the revolution. They did their best to promote new society in every aspect, including art and freedom of artistic expression.
Attached the image of suprematist plate designed by Kazimir Malevich by ex Imperial Porcelain Factory from early twenties (Leningrad porcelain factory). Also, new Soviet government issued silver coins of the same fineness as imperial coinage i.e. 900 (image of one ruble 1921 - 1922).
Unfortunately, they sunk into sterile social realism in art and dictatorship in government, ending in religious backwardness.
This is how you calculate fineness based on the fact that 96 zolotnik is 100 % (pure silver).
96 = 1000
84 = X
84 000 /96
X= 875
Regards
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