We come across a rare mint condition Sylvania labeled, Tung-Sol made sleeve of 6550 three hole grey plates. All tubes are brand and stunning. The Tung-Sol 6550 3 hole grey plates are linear, powerful, and deliver that great American mid-range. This tube was the US answer to the GEC KT88 and was used interchangeably. The Sleeve is made up of 5 6550s, and all are perfectly matched.
All tubes are tested on a AT1000 computerized tube tester at real world operating voltages (450 volts in the case of the 6550), one tested tubes are also matched at those voltages. For power tubes we match based on EM first and then GM. For small signal tubes we match based on GM then EM.
Please be aware that vintage vacuum tubes are antiques and carry no guarantee or warranty. We provide a sheet explaining what you purchased, your test results for your tubes, and if need be can provide photographs of the tube on the tube tester before we pack and ship them.