This exhibit is a PY88 marked CPC and 'Foreign'. CPC was a reseller of electronic componemts and the box that this valve came in says that the valve was made in Japan.
The PY88 is an efficiency diode for use in television line scan systems, where stored energy in the inductances is returned to the HT rail capacitors. The maximum peak inverse voltage (PIV) rating is 6,600 Volts. The peak anode current is 550 mA. These diodes require a very good heater cathode insulation and the PY88 is rated at 6,600 Volts.
The anode is carbonised on the outer surfaces but the inner face is bright as can be seen from this end-on view. The anode is basic an X in cross section with the additional flanges as shown.
The two sheets forming the anode are stitched together.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 78 mm tall.
References: Datasheet & 1040. Type PY88 was first introduced in 1958.