You have a Gold Lion KT88, and it looks fairly genuine. Same tube as the GEC KT88. Possibly worth up to a few hundred bucks per tube, if you have a matched pair or quad that you can get away with selling as "NOS" on Ebay.
Not sure what singles are worth. I have 7 of the GEC ones pulled from scrapped lab equipment. I was able to make two matched pairs for my stereo, and I have three left over that don't match each other at all.
They make my hi-fi sound wonderful, and I couldn't honestly sell them as NOS, so I intend to keep them.
I also have one GEC KT66 pining for a mate.