I was following this one but didn't bid.
L. Leroy et Cie had a tradition of anti-magnetic watches, ending with marine chronometers built entireley of non-magnetic materials. I'd guess it has a soft iron inner case, but who knows...
I'm increasingly surprised at the range of offerings from Leroy, ranging from frankly indifferent middle-of-the-road wristwatches through to ultra-top-end pocket- and wristwatches, and from marine chronometers to uber-precision observatory clocks.
I still want one of the Peseux 260 wristwatches they made, but they're few and far between.
It's a shame there's not more info about them. I've been researching them off and on for a few years, but there isn't much out there. They still have all their archives, so the source material is there.
nick