The 1H5GT is a dry battery diode triode for receiver use. The 1H5GT is the same valve but on an IO base. In a TRF receiver the diode would provide AM signal demodulation and the high μ triode would be the first audio voltage amplifier.
The Sylvania name and the American Government procurement code of VT-177.
The base of the box anode. The gettering covers the rest of the envelope.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 54 mm tall.
References: Data-sheet, 1040 & 1043. Type 1LH4 was first introduced in 1940. See also1940 adverts.