5AR4 ( GZ34 ) NOS MULLARD for HAMMOND, Blackburn plant, 7 Notch Copper Plates, Matched Pair Tubes Rectifiers Made in GT.BRITAIN Mullard's New Old Stock 5AR4 (GZ34) tubes represent the ultimate in performance and reliability for audio enthusiasts and radio amateurs. Manufactured at the renowned Blackburn factory in Great Britain, these rectifier tubes are a treasure for any collector or engineer. The distinguishing feature of these tubes is their 7-notch, copper-plate construction…