The PCC189 is a a VHF variable-mu frame-grid cascode double triode with low impedance and high gain. The technical specification specifically states that it is built with frame grids. The valves are variable μ types for use at RF as AGC controlled devices. The low voltage high current suggests a low noise design, probably as the front end stages in a television tuner. The low anode voltage suggests both stages used as a cascode (series connected) amplifier.
The working part of the anode is pushed forward to close to the grid, what can be seen is one half of one anode - the heat radiating element. The bright plate behind the anode is the inter-section screen.
Between the two halves of the anode the frame grid can be seen but individual wires can not be resolved. The lower mica is in fact a pair and this extra thickness greatly reduces the long term effects of vibration.
The thin glass tube envelope is 21 mm in diameter and excluding the B9A base pins it measures 46 mm tall.
References: Data-sheet & 1040. Type PCC189 was first introduced in 1960. See also1960 adverts.