Item Tag: 510

De Forest Audion 510 Audion ( NOS Antique Vacuum Tube). Designed primarily as a. 🇺🇸 DeForest Audion MADE IN USA 🇺🇸. 1927 NOS DeForest Audion 510. Made 1927 to 1929. ( AUDION 510 THE GRAND-MOTHER OF HIGH FIDELITY).