The 1LA4 is a battery audio output valve. With a 27,000 Ω load the output can be up to 115 mW. The 1AL4 is high impedance pentode. It is a Loctal based valve and the 1A5G is the octal alternative.
This exhibit has lost the metal base skirt and spigot that would cover the evacuation tube. At the top can be seen moulded into glass the pip that indicates pins one and eight.
Philco looking for repeat business. Or admitting that the valve will need replacing at some point.
The anode within and part of the words Loctal and Made in USA.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 55 mm tall.
Reference: Data-sheet. Type 1LA4 was first introduced in 1940. See also1940 adverts.
