As the extremeGammon analysis below shows, this is a redouble and a drop.  Now, here, is what is so complicated:  if you change the score slightly, it's a big take, and change the score a little more, it's not even a redouble.  This position is extremely volatile and there are many gammons, so a small shift in the take points and value of gammons can completely change the cube action for both sides.