Strong matching pair Sylvania JAN-CHS-6SN7 GT/VT-231 tubes from the 1940s. Purchased 11/4/2015 from Brent Jesse (audiotubes.com) for $199.00 (see photo of invoice) as back-up tubes and never installed in my system. Gm results between 3250 and 3350 (see photo of tube boxes). According to Brent, NOS Gm is anything above about 3000, and expected life is 5,000-10,000 hours. Condition conservatively listed as Very Good. Please call with any questions (603-643-2683).