The MVSG from Cossor has a mirror finish inside the envelope from the magnesium gettering. Externally the envelope is covered with a metallic paint to add to overall screening.
Introduced in 1932, Cossor in 1935 describe the MVSG as a special variable-mu screened grid valve. The special feature being the control of volume by altering the grid bias. It is clear that variable-mu technology was still relatively novel.
The classic envelope is 42 mm in diameter and, excluding the B5 base pins, is 120 mm tall.
References: Datasheet & 1043. Type MVSG was first introduced in 1932.
Absolute Maximum Operating Conditions¶
Updated February 02, 2013.