The 1EP1 is a small precision oscilloscope tube with a flat faceplate.
The base has 11 pins. The insulated heater coil in in the centre of the image entering the cathode tube. The emissive coating is on the top of the cathode cylinder only. The surrounding tube is the first anode or grid. The anode cylinders combine to make an electron lens as well as accelerating the beam.
The hollow anode cylinders have small holes in end furthest from the cathode.
The presion flat faceplate.
The circular ring looks like a phosphor burn.
The end window envelope is 32 mm in diameter, and excluding the base pins is 90 mm tall.
References: Data-sheet. Type 1EP1 was first introduced in 1956.