First made in 1924, this tube has a green stripe painted on the side of the glass, from the base to the tip. This indicates that the tube is for Low Frequency use. The stripe measures about 3 mm wide and overtime, in many cases, the stripe has worn off..
Bibliographie
British Radio Valves - The Vintage Years: 1904-1925 P. 50, 87 & 115
ARDE_LF: Fin Stewart
Fin Stewart
Just Qvigstad
ARDE_LF: Banneitz, TB der drahtl. Teleph. 1927
Anonyme 15 Collectionneur
