Chinese made E810F 7788 tubes. Some are branded Telefunken, others National.
E810F is a long life, low noise, shock and vibration resistant pentode with very high transconductance ( Gm ~ 50,000 umho or 50 ma/V). Price is per tube. Limited quantities available of this item. This item is shipped from Britain, in North America or Asia please allow 2 to 3 weeks for delivery.
Data on this item: http://www.tubezone.co.uk/pdf/e810f.pdf