I have a copy of Van Gogh's "Avenue of Poplars." I've had it for 30+ years and it was old when I bought it. I've never taken it from the frame. It's quite interesting and looks like it could be an original pencil and ink but it is not. There's a C within a circle on the bottom left followed by the letters VG. I'm trying to establish some worth but the only copy I can find is an oil reproduction and this is not a painting. The technique is pencil and ink. The style is realism and the material is paper. It was done in 1884. Any words of wisdom?