YOU ARE BIDDING ON A VINTAGE CIRCA 1950'S (COULD BE A LITTLE LATER) MULLARD TUBES BROCHURE DESCRIPTIONS;TYPE, EIA TYPE, BASE, DESCRIPTION, HEATER, LIMITING VALUES, AND TYPICAL CHARACTERISTICS. ALSO MULLARD TO EIA. CROSS REFERENCE, BROCHURE INCLUDES THE EL-34 ECC83 WHICH ARE PICTURED AT THE TOP INSIDE. IT IS IN EXCELLENT CONDITION ONLY VERY LIGHT WEAR. PLEASE LOOK AT ALL PHOTOS AND ASK ANY QUESTIONS YOU MAY HAVE. REMEMBER THAT I SELL MOSTLY ANTIQUE AND VINTAGE ITEMS AND THAT THEY ARE MOSTLY LIKELY NOT BE PERFECT DO TO THE NATURE OF THEIR AGE. IF YOU HAVE A PROBLEM PLEASE CONTACT ME BEFORE LEAVING FEEDBACK.