High quality beam tetrodes 6P3S-E (6П3С-E) used in output stages of low frequency amplifiers. Made in Reflektor plant in the 80's for export. Russian equivalent of 6L6GC and 5881 tubes. Tubes were fully tested on L3-3 precise tube tester and matched in quads. Military quality, long life - E tubes (not less than 5000 operating hours), gold plated first grid. NOS/NIB tubes. Boxes may have some longer storage marks.