S.N.Ammosov, the picture

[NikolayA]

Good afternoon.
I have a picture of Sergei Nikolaevich Ammosov, 1881. Size - slightly less than A4 paper.
What is the price such a picture ?
In my view watercolor, but I'm not good in the materials. Oil can tell , and nothing else < - ~ 2 ~ ->
And where is the expertise to do (SPB )? I was sent to the Russian Museum . It makes sense to go or money?

Thank you,
Nicholas