Hi Clint,
I thought of that, but sadly it was shipped with an original Varta PX625 mercury battery. I also tried a wein cell zinc/air 1.35v battery which should have done the trick.
It is odd - it does seem like it's behaving like it would had the meter been recalibrated, but for a lower voltage cell, not a higher voltage.
I await the seller's response - he's talking with his Leica expert, Mr Willem van Manen (I think) of the the Netherlands. Has anyone had any experience with him?
Best,
Rob