The X41 is a metalised triode hexode frequency changer designed for AC mains receivers. The X31 was designed with a heater for universal mains (AC/DC sets) but is otherwise identical.
The interesting feature of this exhibit is the zinc paint. It is still in one piece but has become detached from the glass and has expanded away from the glass in places.
The Osram brand name.
The top of the valve with the metal paint standing away from the glass that it was originally sprayed on to.
The classic envelope is 48 mm in diameter and, excluding the B7 base pins, is 113 mm tall.
References: Data-sheet & 1043. Type X41 was first introduced in 1935. See also1935 adverts.