The Mazda UU60/250 was an indirectly-heated HT rectifier introduced at much the same time as the AC/Pen output pentode (1930) and intended to delay the delivery of HT until the cathode of the AC/Pen had warmed up sufficiently to draw current.
Type UU3 is essentially a redesigned UU60/250 and is interchangeable with it. This exhibit looks just like the UU3 whereas the other UU60/250s have a quite different construction that is much closer to the way rectifiers developed.
This full wave rectifier would have been used in domestic broadcast radio receivers. No values of reservoir capacitance or series resistance are given in the literature.
A side view showing one of the stout wire supports that holds the top of the anodes firm.
The two anodes seen face on the anode supports struts can be seen to be fixed to a collar that is screw clamped to the pinch stem.
The balloon envelope is 58 mm in diameter and, excluding the B4 base pins, is 105 mm tall.
Reference: 1043. Type UU60/250 was first introduced in 1929.