This new old stock-testing Matched Pair National Union 6V6GT Black & Silver Glass, Black Plate output tubes was tested on our Maxi-Matcher 2 for shorts, gas and transconductance.  There were no shorts or gas. Transconductance measured:

Tube One:  23.3 milliamps / 2610 micromhos (Unbranded base but stenciled with NU manufacturing codes 247 5039; 6V6GT PB on glass)
Tube Two:  21.4 / 2460 (Unbranded base stenciled with manufacturing codes 3R09 337; 6V6GT AQ on glass)

Measured with 400 volts on the plates and a bias of -36 volts. New US-made 6V6s typically test with plate current from the mid teens to mid 30s with transconductance from 2200 micromhos or so.  

(NOTE: Newly manufactured 6V6s also typically test from the mid-teens to mid-30s with transconductance from 3000 micromhos; because of the massive variety of this tube type and differences between new-production Eurasian 6V6s and older American varieties, readings such as this are common).

These tubes have been tested for the high-end stereo/audio user and sound tested on our shop amp (see pics). Pair are tight on bases with no debris or rattling.  Pair are black & silver glass with black plate.  Tightly matched electrically.  Tube One has a crack on base that does not effect sound performance.

Checkout our other tube listings for your equipment needs.

Shipping is USPS Ground Advantage with tracking in the United States; Priority Mail is an option.  International sales shipping via eBay International Shipping.

Package weighs ten (10) ounces.

Combined shipping always welcome on multiple orders.

TUBES ARE GUARANTEED GOOD AND IN WORKING ORDER AT SHIPMENT. TRANSIT VIA POST CAN DAMAGE TUBES. THIS IS NO FAULT OF OURS BUT THE THIRD PARTY ENTITY THAT IS DELIVERING ITEM(S) TO YOU, I.E, USPS, UPS, FEDEX, YOUR NATIONAL CARRIER IF INTERNATIONAL, ETC. PLEASE INSURE THEM! WE CANNOT GUARANTEE FAILURES ON YOUR EQUIPMENT AFTER POWER UP AS THERE IS NO WAY TO ASCERTAIN HOW TUBES WILL INTERACT WITH YOUR ELECTRONICS; NOR IS THERE A WAY TO DETERMINE WHETHER THEY MAY HAVE FATAL FLAWS IN TUBES THEMSELVES! THESE ARE USED VACUUM TUBES AND TIME MAY HAVE TAKEN A TOLL ON THEM OVER THE MANY YEARS SINCE THEY WERE MANUFACTURED. WE CAN ONLY TEST FOR THE  PARAMETERS MENTIONED ABOVE IN ONE OR MORE OF THE FOLLOWING EQUIPMENT WE USE FOR MEASURING: TV-7/U, JACKSON 648 & MAXI MATCHER 2.