The V99 is a low μ triode from the 1920s. It is an American valve and is fitted with a stub-pin bayonet UV base. The V99 was designed to have the filament supplied by dry cells and has a low consumption making it suitable for portable radio receivers.
Philco also made the X99 which has the same triode mounted on the later UX4 base.
The tubular envelope is internally silvered by the gettering and the inside is obscured. The locating pin for the bayonet base is seen on the right.
The base with the short stub pins. The central lighter colour material is part of the valve but the blue specks are the remains of the blue-tac that was once holding the valve for display.
The wide glass tube envelope is 26 mm in diameter, and excluding the base pins is 80 mm tall.
Reference: Data-sheet. Type V99 was first introduced in 1925.