How heavy is a standard military bullet-proof vest?

Hi,

I believe and have researched that the mark1 helmet (used in WW1) weighed 0.54 kilograms(1.2 pounds). This mark 1 helmet was dubbed the Brodie Helmet, It was deigned and patented by Briton John L. Brodie. Originally the helmets before it were manufactured from cloth and could not stand modern weapons. After a while the British war office realised the dire need for a new type of helmet.

I hope this helped you and you learned a bit more information regarding body armour and weapons.