This is a Dutch auction for GE 50C5s.
These tubes have matte black plates with two horizontal ribs and a vertical groove on each wide side of the plate. In addition, they have copper support rods and what looks like a small trap door on the very top of just one side.
They have been tested on our Paul Hart-calibrated TV7/U (where minimum (65%) is 45) and have the following values in descending order: 76, 68 and 65.
You must indicate the quantity you want. Etsy will indicate how many are available. You will always get the-best-testing tube(s).