The 3A4 (DL93) is miniature output pentode is specified for both audio and transmitter use. For a small dry battery valve 1.2 Watts output in the HF range would be quite an achievement.
The RCA logo and a view of the two wire grids. The metal structure inside the anode cylinder is the beam plate. This pentode is made as a beam tetrode.
The country of origin.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.
References: Data-sheet & 1040. Type 3A4 was first introduced in 1945. See also1945 adverts.
