The 3BP1 oscilloscope tube has a medium persistence green phosphor and a three inch diameter screen. Actual maximum diameter is 76 mm.
The 3BP1 design dates to the mid 1940s but was a popular choice for home construction oscilloscopes up to the 1970s.The main image shows the electron gun, the etched identification and the internal colloidal graphite coating that acted as the final anode.
This exhibit was made for the US army and Navy.
The curved screen. The painted letters are FB-367 and this matches the original box.
The gun and electron lens is held at precise distances one to another by the ceramic spacers on the supporting rods.
The deflection plates are located under the coated bell of the envelope.
The B14A base pins are in an unused condition.
The paper label from the original carton. This box measured 140 mm square and 365 mm long and was made of substantial cardboard. Inside the tube was held in a shaped card wrap that had a handle formed at the screen end to allow the tube to be safely withdrawn from the protective case.
The wide glass tube envelope is 51 mm in diameter, and excluding the B14A base pins is 235 mm tall.
Reference: Data-sheet. Type 3BP1 was first introduced in 1944.