Ostar MS18
AC Amplifier Tetrode
1933 (Austrian)

Ostar made tubes in the early to mid 30's with high voltage heaters. Most of their tubes were available with filament ratings of 110-125V, 150V, and 220-240V. The MS18 shown here ran at 220-240 Volts and 24 Ma. A number of their tubes used the mesh outer shield shown.