Hi Hazel, Just a quick note: you misread my first name. it's ilia, not llia.
What I can add to the previous message, is that my great-grandfather's family were [also] jewelers before the revolution. Afterwards, in the 20's, part of the family moved to France, but they were mostly women, as well as his brother, but none kept the "de notkine" surname.
Those who remained in the soviet union are all that I know of. My grandparents were still writing their surname as "de-Notkin", and it was only my father (born 1965) who started writing it as "Denotkin". It is quite probable that the "de" part was added to the surname "notkin", yet I have no clue how or why. A guess by my father was that it was added in France, yet it would then be carrying the meaning "of Notkin", which would have to be a region or a village, nothing I have ever heard of. As for Notkin being a Jewish name, I find it quite probable since almost everyone in my family is Jewish, myself included. I said almost everyone since my great-grandmother was Russian, so it was this word that remained in the "nationality" section of the passport, what was quite useful during the soviet era. As for Notkin being a POPULAR Jewish name, I am not certain, since I have never seen this surname.
Up to my grandfather, no one in my father's side has had any brothers, myself excluded. I have a 6-year-old brother, named Leo Denotkine (after my grandfather). This fact means that the surname Denotkine was preserved as a straight line for at least a century (in my family - that is).