General Electric GE 12AT7 ECC81 6679 Vacuum Tube Premium NOS NIB Hot-Stamped Bases These tubes have steel support

These tubes have steel support rods and top

It is probably a Mullard

new in box GE 6AS8 tubes tested to spec on our Paul Hart-calibrated TV7/U

OEM-BRANDED black glass 6K6GT tubes was tested on our Maxi-Matcher tube tester with 325 volts on the plates and a bias of -36 volts

These 11 RCA gray glass 6D6 tubes were tested on our Paul Hart-calibrated TV7/U for shorts

General Electric GE 12AT7 ECC81 6679 Vacuum Tube Premium NOS NIB Hot-Stamped Bases These tubes have steel supportThis new old stock, new in box industrial grade GE 6679 12AT7 dual triode was tested on my Hickok 600A for shorts, gas and transconductance. There were no shorts or gas. Transconductance measured 4100 3400 micromhos. (New 6679s typically test within 1. 5 standard deviation of 4000 micromhos; minimum (65%) is 2600). It has gray, wing plates; a top, slant D getter and excellent flashing. I am playing them in my Bottlehead Crack headphone amplifier as I