Earlwb and the rest of the group back in 1949-1950 when I was in high school Pop was a pharmacist he got medical ether USP the stuff used in the OR for anesthia it came in small metal containers
made I think by Merck the top was sealed under the cap with a metal disc it appeared they had a small chunk of copper in the can to prevent peroxides , he would punch the
top and mix with mineral oil for my drone 29 martin
my quess is they did not want to take a chance on peroxide formation which could be irritating to the lungs if inhaled