EL34 Mullard Platinum Matched Quad NOS NIB Blackburn Xf4 1979, rebranded Philips

Mullard Blackburn EL34 / 6CA7 Platinum matched quad (4) tubes

Platinum matched quad within 5% of rare Xf4 type, rebranded Philips in genuine yellow Philips boxes. 

I had few 100 pcs boxes of these gems, so all quads I offer for sale are perfectly matched, within 5% or less. 

Two slots on plates, four support points on both spacers, folded plates (stapled), copper grid posts, black base! They are made in Mullard Blackburn tube plant, and etched codes the same. The codes are clearly visible on photos Xf4 B9K4.