Kilner Bro's sold out in the late 1930's to The United Bottle Company which became United Glass, which became Ravenhead and then Rayware. All screw top bottles Original, Improved and Dual Purpose jars carried the Kilner name the jars with the Red-Orange plastic screw rings were named Ravenhead Kilner and these were the last of the screw top Kilner jars.
Ravenhead now market Ravenhead Kilner clip top jars made somewhere in the far east.
If anyone wants spare parts for the old screw top Kilner jars or reconditioned jars they are available at
www.kilnerjarsuk.co.ukMy personal experience is that screw top jars are much easier to obtain a good vacuum seal with than clip jars and much safer I find it quite dangerous trying to close the clip on a boiling hot jar full of fruit.
Peter