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

Well, you could make both of them float on water or something similar and see if one of them points North.
Or you could heat up one of the bars and see if they still stick to each other. If they don't anymore, the one heated up was magnetic.
Or you could pass it straight down a copper pipe. If the fall is cushioned, that one is magnetic (Lenz's law).
Or you could pass each bar through a coil of copper wire and measure if there's a charge generated by the work you put in.
Or you could cheat and use a Magnetic field viewing film.