The 1299 inside is an American battery amplifier pentode. The all glass designs did not emerge until 1938, the first reference in the Brimar manual is 1950 as the UK did not make Loctal valves until after 1945.
This exhibit is sealed into the original carton supplied to the US military and is dated 11/1943. The 1299 shows the form of the valve and has the 1299 on the dome.
The dome showing the 1299 Type designation.
The base: the spigot locks the valve in the holder, hides the evacuation pip and can be used as a terminal if required. The shaped inner sleeve has hooks that locate into flap across one corner of the outer. Removing the valve tears the carton showing that it has been removed. The pins are accessible to allow for testing whilst still sealed in the box.
The box measures 35 mm square and is 97 mm long.
The printed face.
The other printed face. The remaining two faces are blank. For a government procurement contract 'plain vanilla' packaging was all that was required. Commercial valves had makers branding on them as per .
The wide glass tube envelope is 28 mm in diameter and, excluding the B8B (Loctal) base pins, is 54 mm tall.