M-OV's first indirectly-heated HT rectifiers were the MU12 and MU14. These were in fact the same valve but only a minority of each production batch were good enough to withstand the full rating when tested. These few were labelled MU14 and here the brand is Marconi.
The twin anodes. The cathode tube is connected by a tape to one side of the heater.
The shaped anode has a side flange for greater radiating area. The anode is stitched together and the support runs between the sheets.
The classic envelope is 45 mm in diameter and excluding the B4 base pins, is 105 mm tall.
References: Data-sheet & 1043. Type MU14 was first introduced in 1933.