744
xkcd #2944: Magnet Fishing
(imgs.xkcd.com)
Alt text:
The ten-way tie was judged a ten-way tie, so no one won the grand prize, a rare fishing monopole.
Most of Canada's small coins respond to magnets. Not sure about other countries.
Edit: Or even better, old ferromagnetic coins or forgotten tools from past ages if you're in areas of the old world
Interesting! TIL! Thanks.