This record consists of 15 tubes, two of which are labeled 12AU7A. The 12AU7 is a medium-mu twin triode in a miniature nine-pin glass envelope. The 12AU7As are made by Sylvania; the rest are from Westinghouse. Each tube in this record has a unique number stamped in yellow ink around the envelope. Six tubes have an off-white dot painted on the top near the tip; four have a yellow dot; three have an off white dot and green dot; one has an off white dot on each side of the tip; and one has two off-white dots on top of the tube and a green dot on the side of the tube near the top.
Printed in silver ink around the glass envelope of 13 objects.
Printed in silver ink around the glass envelope of two objects.