1955 WOW! I didn't think they were around then. I have a Medos programable, which was installed in December 1998, replacing the previous set-pressure one. I have fallen on my back at work (slipped on a wet floor), smacking the shunt on the concrete , and no damage occured. MRI was A-OK, I don't recommend it though. MRI's or strong magnetic fields will mess with the settings, and re-set it to the lowest level. You will want to have the calibration checked by your neuro after a scan. They are pretty darned durable.

David