Help evaluate the picture
 

picture got in nasledsvo husband, I know that bought in St. Petersburg at the Hermitage employee, the figure marked on the marble, the heavy bronze frame, signature Agnese Postempski 1858.

Bought from the Hermitage staff should immediately check on the basis of Ministry of Culture, "Attention, search!"
 
What size and weight of work?

checked, nothing.

Добавлено через 3 минуты
The size of a
picture in a framework makes 40sm in height, and 32 sm at length. The
framework at width 5 sm/ Marble in the thickness 10 sm,

Добавлено через 3 минуты
The size of a
picture in a framework makes 40sm in height, and 32 sm at length. The
framework at width 5 sm/ Marble in the thickness 10 sm,

If you have successfully dismantled a signature, because
the photo did not understand, then it may be Roman Postempski (1808-1858).
Here is an example of his work.
On Polish auction in 2008 it was estimated at 16,000 zl.:

http://www.rempex.com.pl/wydarzenia/...y/6079-madonna

While at your work the first letter "A" clearly visible ...

Able, therefore, was an employee Hermitage.
It remains to find out who this Agnese Postempski.

And the size and weight of work?
This is a fresco or what?

By the way the story is called: "Madonna on the crescent.

Crescent - the symbol of the Church

no it is not novel I read about him, is clearly visible inscription "Agnese", the size of picture 40cm in height and width of 32 cm and weighs about 4 kg. (along with a bronze frame)

This is most likely enamel (and not very bad).

In Durer, have a similar story.

Madonna all have, but the plot is not quite that. In Durer is "Mlekopitatelnitsa (Nursing Madonna)."
Posmotrtie Domenico Tibaldi - Madonna on the crescent.
What is enamel? Kidding?
    Painting on marble, and indeed very good.
 Although now the fashion-icon write on a stone,
but in the 19 century are extremely rare painted marble slabs in bronze frames.
At some auctions in Europe have seen similar. 2 or 3 thousand euros. I do not remember, was the author or not

Ficke, You can take the work out of the frame and take a photo of the back side and end.