Thank you for your answers child and zolotnik!
Just to learn a little bit too, what makes you think this cup is authentic? Is that only wisdom and experience or...? Is there a concrete approach that everybody could use?
before you start to collect something like Russian silver, you must know the history, background, laws, rules, marks and what you really want. Than after starting slow (unexpensive) with small objects, having done your homework, watching the market (esp. the fake market!), having bought some relevant books, visiting some fora - you will get some experience (positive and negative) and can start to broaden your collection. Don´t be greedy, if you have doubts - go away. Don´t believe the phantastic storys sellers tell. Try to get an own opinion build on knowledge. You will learn every day something new.....and most of all: communicate with other collectors - they had made all the mistakes already which are waiting for you.
Thank you for your advises Zolotnik! I agree with you in particular about history, laws, etc... that I do not know very well! I was specialized in french silver hallmarks and recently interested myself in foreaign silver (especially russian silver). So I've got to proceed step by step!!!
I hope to come back soon with another item... mainly a good one! ;-) I have been lucky with my previous 6 items which were batch sold... Luck of the rookie!