Although many manufacturers were still using cardboard caps and paper tissue for jam jars in 1955, from as early as 1905 Fred Duerr was pioneering the method of vacuum sealing jars - the process allowed the jam to keep indefinitely. Our Chairman, Tony Duerr has two vacuum packed jars from 1903 in his office. The jam should still be edible... but so far he has resisted the temptation to compare the flavour with today's batch!