The L77 triode was specified as both an amplifier and an RF power valve. In the latter role it would deliver 5.5 Watts. With a very small envelope volume, this would make it ideal for hand portable equipment. In larger apparatus it could deliver enough drive power for much larger PA's.
The anode end seam with the getter holder above.
The Marconi brand label for this M-OV valve.
The thin glass tube envelope is 18 mm in diameter and has an overall length, excluding the B7G base pins, of 46 mm.
References: Data-sheet & 1040. Type L77 was first introduced in 1951. See also1951 adverts.
