Old school Bird sexing

Hi all. I was taught a method to sex a bird,human,animal,whatever by a pigeon keeper/racer. This method is non invasive, free, and so far has been accurate.
See attachment!
I know it looks horrible! It is a small magnet attached to a string. I will make a better one soon.
The way it works is simple. Hold the string so the magnet can swing freely. Get the magnet as close to the subject,without touching. once the swinging from you placing it stops,you will see the magnet kind of lock on. Hold it still and the magnet will start to move on its own. side to side for male,circle for female. it's that simple! Every human I've tried this on has had the same results. Every bird likewise.
Practice on humans as they will sit still more readily. Once you have mastered,try it on your bird! I have met more than a few "male" DNA sexed birds who laid eggs!
Rosie my grey was a re home. from a shop that apparently keeps crappy records.Named Tiki and a male. The bird told me her name was Rosie. Was aggressive to me until 2 minutes after I addressed her as Rosie. The magnet says he is a she!

Interesting concept!