This is a Electron tube by Realistic Lifetime.  This is one of many tubes I purchased at an Antique auction some 20+ years ago of a TV/Radio repairman's bag that had many different tubes  It is untested. The tube code is #6KZ8.   I hope you can tell from the photos if it looks viable. I listed it as used because it is old and I couldn't test it.The tube was in a closed box so I don't think it was used.