The picture is 13" H x 21" W. It is believed to be a Lithography Signed by William Gropper.
Hello again Reza,
Thank you for all of your inquiries with Mearto. This item appears to be a lithograph by William Gropper (American; 1897 – 1977) titled "The Summation." The print is signed in plate and by hand. It is also marked "artist proof" to the lower margin. The image is one of several similar images by the artist with the same title. Gropper was a well known cartoonist who was a radical artist, producing very political left-wing images. In today's secondary market, a fair market estimate of $50 - 200 would be assigned to the print. The estiamte provided is based on recent auction estimates and results of this print and other similar prints, signed by Gropper and marked "artist proof." Thank you very much.