Can you solve the MAGNET RIDDLE? ft YouTube CEO Susan Wojcicki

If the magnetized iron bar is a simple dipole, you could check different orientations of both bars relative to the other one. As the magnetic force is (much) weaker halfway between the north and south pole, one could put the bars into a T-shape orientation towards each other. If the bars are attracted to each other more, the "lower" part of the T is the magnet. 
Greetings from a german physics student ;)