This is Matthew Brady "carte-de-vistie" photographic card, imprinted on the verso of "Brady's National Photographic Portrait Galleries. No. 352 Pennsylvania Avenue, Washington D.C. and Broadway & Tenth St., N.Y."
"Gen. Grant" written in ink on mount below the image of the General. The portrait of a rather young-looking Grant, possibly just after being appointed overall commander of U.S. armies in the field.