Vintage Philco and MajesticType 45 vacuum tubes. Which is a celebrated directly heated power triode introduced in 1929. It was extensively utilized in the audio output stages of 1930s console radios and is highly sought after by modern audiophiles for its exceptionally clean and musical single-ended audio amplification. These were an estate find. According to historical data sheets like the Tung-Sol 45 Manual, the standard operating parameters include. Filament Voltage: 2.5 V (AC or DC). Filament Current: 1.5 A. Maximum Plate Voltage: 275 V. Average Plate Current: 36 mA. Amplification Factor (Gain): 3.5. Maximum Power Output: 1.6 to 2.0 Watts. The base features a standard UX-4 4-pin arrangement. When looking directly at the bottom of the base with the two larger pins pointing toward you. Filament Pins: The two larger/thicker pins (Pins 1 and 4) carry the 2.5V filament supply. Plate Pin: One of the thinner pins (typically Pin 2) connects to the high-voltage anode. Grid Pin: The remaining thin pin (typically Pin 3) serves as the signal input grid. The handwritten text “FIL OK” on the glass bulb indicates that the filament has been tested for electrical continuity and is not broken. I didn’t test it, but I believe it’s in good working condition. Please view photos for more details.