The tube at left is branded Lewis and Kaufman "6Y5GT". Lewis and Kaufman was an old US maker of transmitting and industrial types. They NEVER made receiving tubes. Someone else owns the brand name and has used it to rebrand many types. This is an odd case. The tube branded 6Y5GT has a shouldered bulb and a 5 pin base. The "GT" suffix would indicate a tubular T-9 bulb and an 8 pin octal base. Close examination under good light revealed that this was really a rebranded type 84 tube.
The 6Y5 was originally introduced by Majestic, and it is a 6 pin, spray-shielded rectifier. An original Majestic 6Y5 as well as a slightly later Sylvania substitute are pictured at the center. The 6Y5 was also sold without the shield by other manufacturers. A correctly branded type 84 is at the right.
Obviously, since it does not even have the same number of pins, the fake is not a usable sub.