Just to make people aware of the danger of handling old military spec fire extinguishers, a member here had an incident when one discharged http://www.warrelics.eu/forum/equipm...10/#post834833
They can contain some quite toxic chemicals such as bromochloromethane - PubChem
My advise would be to leave old extinguishers well alone unless you know it's empty or it's a harmless water extinguisher. Cheers.