It seems to me this folk art tabletop chair may have been made specifically to house this particular photograph (real photo postcard), as the dimensions of the card is longer and more narrow than your typical rppc. And a photo of a chair set within a chair seems quite right, too! Clearly it has lived here for quite a long time, as removing it reveals a much brighter tone of stain. No nails here, rather the chair was pieced together of interlocking parts, and turning it around reveals fancy cutouts on the back that the picture obscures. 

12" tall x 6 3/4" wide x 5 1/2" deep and in very good condition, with some craquelure to the finish as shown in details. As noted, when rppc is removed, the stain is a little lighter behind it from the way the rest has aged. Easy to change out the photo, of course!