This object consists of an evacuated glass envelope surrounded by a magnetic shielding. Two concentric circles of pins project out of the bottom of the envelope. The inner circle consists of nine pins, and the outer circle has 17 pins. The device is a decade counter that can be configured for several applications, such as a staircase generator, frequency divider or counter. It is capable of running up to 2 MHz. Unlike the 6700 Trochotron tube, which has an external magnet, the BX-4000 has ten circular magnet rods within the glass envelope; these also serve as the target electrodes. This object is enclosed in an unmarked box with the tube description handwritten in ink on the top.