The 13 is upside down in relation to the assayers mark. The other way it looks like EI. This is what the makers mark looks like under the magnifying glass, There is a notch after the 3.
Mart... Thank you for sharing your knowledge, it's very interesting. It actually belongs to a friend who found it at the back of the spoon drawer, a great aunt gave it to him years ago and he forgot all about it. I'm glad you solved the inscription as being the proverb.
Thanks very much Mart for the Russian proverb, I had a go translating it from Cyrillic but no chance.
Thanks Qrt.s for identifying the makers mark. I take it the assayers mark is unreadable then. At 5" it seems too long for a tea spoon, would this be a soup or serving spoon