As they say, experiment is the base of science.
So, I carried out an experiment with my collection. All my blades passed 2cm away from a compass. Observations:
1. About 40% of them moved the needle.
2. No matter if the blade was antique wootz or 20th century factory made.
3. No matter if the blade is sort or long.
4. Most of the magnetized blades had north polarity in the tip.
5. Some long blades look like they change polarity in their length. They changed the direction of the needle few times as they were passing by.
6. And the winner is… an ottoman kard! This thin 6 inches blade forced the needle to do circles like maniac! Second winner a Caucasian kindjal that made the compass to do a full circle.
Conclusion? The magnetized blades are a funny hour. Sorry mystics. The truth is still out there