The image shows four perfectly matched 6CS7 tubes (a so called ‘quad’) from the American producer Sylvania, which is easily seen from both the brand name on the boxes and the characteristic logo consisting of af Z-like ‘S’.

The 6CS7 tubes, originally designed for use in tv's, are used in the Leben CS-600 and the Leben 600P, in the SRA-3S headphone amplifier by Japanese Stax, the General Electrics RIAA UPX-003A from the beginning of the 70’s and the 5B7 Bassman guitar amplifier from American producer Fender.

Thus it's both an uncommon and as of 2023 a quite rare tube, especially in matched pairs and matched quads.

The 6CS7 tubes in the image are so-called NOS tubes, where NOS stands for New Old Stock, meaning that the tubes have never seen any use, which makes them further rare and expensive.
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