I'd say it's a knife or scythe sharpener. The black frame is mostly rigid except for small adjustments at the top and the handwheels at the side change the angles of the X-bars, which would correspond to the included angle of the cutting edge of the blade being sharpened.
[edit 5 min later...] Looks indeed like the contraption below, which is a Euro-style knife sharpener. These are on Amazon.
