Figure without attribution

[kirill]

Dear Guru! Help to find out something about this figure:
Author unknown.
Drawing on the skin of dirt, pencil, it seems that the graphite, but it does not shine as graphite, not smeared.
Size 30,5 x39 cm
Established unknown.
No inscriptions and no signs, either the front or the back side.
Good condition, the crack is, but did not showered.
Expert opinion - no
Figure bought by me personally in St. Petersburg on the specific, in 1991, for 50r. By the way is not cheap in those days. I bought it it because he liked the picture, and cool, that on the skin. And always interesting, how often do artists have used the skin as a basis? I have never met. Typically, oil on board ...
I would be grateful for any information.