I did have a couple cheap plastic "demagnetizers" and I have used them successfully on my Omega (see my previous post).
But I cannot get them to work on the Hanhart. Maybe the Hanhart is too well shielded, as it is specified and marketed as "antimagnetic".
So I brought the watch to two watchmakers... both didn't want to touch it because it was under warranty. That was strange to me and I essentially begged them to put it on their demagnetizers and they refused. Maybe they just didn't want any liability for an attempted repair, especially knowing the watch was still under warranty.
So I went to eBay.
First I bought a nice vintage South Bend unit:
Somehow, I remained convinced the watch was magnetized, as it's symptoms perfectly matched that. No beat error, good amplitude, but 40+ seconds a day too fast. I still believed the "antimagnetic" shielding of the watch was just making it harder to demagnetize.
A bit of research showed that push-button "instant" demagnetizers are significantly more powerful that the others. So I searched for and found an old Elimag that was claimed to still be working:
The Elimag is claimed to be very powerful, as it uses a voltage quadrupler circuit, meaning it charges to more than 400 Volts. I pulled the crown out (stopping the watch) and put the Hanhart on the Elimag face down and pushed the button. For the heck of it, I did it again, and then on the side crown up and crown down.
And then tested the watch on my timegrapher.... FIXED! +3s/d face up! Yay!
Watch is working perfectly.
Beware of magnetism. ;-)