The 1LG5 is a battery pentode for use in radio receivers. The base is the B8B or Locktal type that was designed for portable/mobile applications.
The 1LG5 is a straight or sharp cut-off pentode and so for radio use it would be used in TRF rather than superhet receivers. Or it could be used at audio.
The Sylvania logo.
The identification is on the dome. The gettering and continuous anode prevent a view of the internal structure.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 56 mm tall.
Reference: Data-sheet. Type 1LG5 was first introduced in 1949. See also1949 adverts.
