The product is a vintage EICO 6X5GT vacuum tube that has been tested and is in Dad's collection. This vacuum tube, manufactured by EICO, is a specific model that is sought after by collectors and enthusiasts in the vintage audio and electronics industry. Its authenticity and functionality have been verified through testing, making it a valuable addition to any vintage electronics collection.
From dad's huge collection of tubes, where he tested most and labeled them on white box in first picture (usually).