Every tube I've purchased off eBay has been bad. And one pair of very expensive tubes that I purchased here went bad inside of two weeks. FWIW, I only go with the bigger suppliers now. Among them:
www.partsconnexion.com
www.tubestore.com
www.tubedepot.com
www.conusaudio.com
If you don't have a tube tester, and complete confidence in the seller, be careful. NOS tubes are a delicate lot.
All the best,
Howard