Mullard Logotypes

The logos above, engraved on the sides of the valves, were used from the release of the first PM3 and PM4 valves in 1925 until about 1931 when the later logo, shown below and engraved on the top of the valve was used.

From November 1st. 1922 until September 1924, all valves supplied in the U.K. had to bear a GPO approval stamp. These, with minor variations, continued in use until late 1927.

Early valves had the anode indication moulding in-filled with white

Many valves have lost the paper labels, shown intact above.