China made EL504 6GB5 tubes. The tubes are new old stock (date codes are from the 70's and 80's) and from factory egg crates.
Price is per tube. Offers on this item considered for quantity 50 or more. This item is shipped from Britain, in North America or Asia please allow 2 to 3 weeks for delivery. Item is same as PL504 except for filament voltage (6.3V instead of 27 volts) . For data please see: http://www.mif.pg.gda.pl/homepages/frank/sheets/010/p/PL504.pdf