The original 4 gall flimsey was of about the same gauge as a bean can. I think they had a tear off cap much like a ring pull. I read an article once that stated the loss rate on each lorry load from splitting whilst in transit was about 10%. There were heavier made variants with a screw cap for food and water. I think this link might have some info.
http://suncompass.fandom.tv/gear.htm
Ron