I have for sale a vintage CBS Hytron 6SN7GT vacuum tube. It has a "5513" date code indicating production in the 13the week of 1955. It has a bottom D-shaped getter. It has been tested on a recently calibrated B+K 747B mutual conductance tester. This tube tested well into the good range at 105 / 105. This tube was also tested for actual Gm with a Weston 798 proportional mutual conductance tester. The triodes were nicely balanced at 2550 / 2550. A Gm result of 2600 is considered normal on this tester. No triode section showed any shorts or grid emission. Due to age, this tube is being sold as is but guaranteed not to be DOA. International shipping includes required insurance.