Thank's for your answer!

For your information:
I removed the silver stamp, leveraged out the magnet and stuck the stamp back on it.
Everything works still fine!

Kind wishes, Marcus

Is it possible to remove the magnetic part from the gps antenna, or does it have any function beside the ability to pin it on iron surfaces?

In the moment the antenna is disturbing the magnetometer of the "1043_0 - PhidgetSpatial Precision 0/0/3 High Resolution".

Kind wishes,

Marcus