The VMS4B variable μ screened tetrode. It was designed for RF and IF amplification in broadcast superhet receivers and was superseeded by the Pentode and KT valves.
The envelope shape matches Mazda production rather than M-OV and so this was probably not made by M-OV.
See also VMS4 for the earlier 1931 version.
The classic envelope is 37 mm in diameter and, excluding the B5 base pins, is 103 mm tall.
References: 1005 Type VMS4B was first introduced in 1933. See also 1933 adverts.