The THERMALL 500 appears to be a 500 watt dissipation triode similar to the Eimac 3-500Z made for the Thermall company by Eimac. The anode is similar to tubes made by Amperex. The pins are short and stubby and the overall height is less than the 3-500Z. No tube data is known. The EIMAC logo is stamped into the grid shield. The second example doesn't have the Eimac logo and has a different anode and plate cap design.

Length = 5.50" Diameter = 3.38"
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