Help with Ever Ready K30g valve

Can anyone help Graham with some advice on this old valve?

Graham writes: "I have an Ever Ready K30g valve (tube) and your web site was the only one which refers to this valve.

"Is this valve rare and does it have any value?
I have tested this valve on a Taylor 45c Valve Tester and it's in A1 condition. It also looks new with it's original box.

Best regards
Graham Ramsden."

If you can help, please send an email to:
valve@southgatearc.org and we will pass it on to Graham.