Yes Marius, of course all iron is magnetic, but it can still exhibit a weak magnetic field (polarization). So many keris that i have personally handled only move the compass needle just slightly when approaching a compass. Being magnetic and being magnetized are two different things though. By applying a powerful magnet to the keris the blade is magnetized and now has a strong active north/south polarization. The blade become a magnet itself (it can now pick up a steel pin for instance).
Only Alexish made the suggestion that this might be used to judge the age of the blade, an idea he got from a dealer in Singapore. Dealers say a lot of things. I think most of us agree that this is unlikely.
