Here are a couple of shots of the little 3NP4 picture tube that was used in the Scott 6T11 projection TV set.
New 3NP4's came in a cardboard box as pictured and were apparently manufactured in Holland.
This tube is 10 1/2 inches long, aluminized, and does a decent bright sharp picture when projected onto a 20+ inch flat screen.
The funnel on the side is used to pour in more electrons (literally)
this would be for the high Voltage connection 25,000 volts.
You can see a line burned into the face of this new tube and thus scan failure protect was invented. Either horizontal or vertical failure can burn in a line as the high voltage is a separate power supply.
Jack will come up with something to trade for this (I'm still looking for knobs for a Admiral 7") or something, but I am keeping the box.
I last fired this tube up in 1992 and according to my note in the box it had a perfect picture. You will note no raster burn on the face.
The face plate is convex and matches the first mirror which is concave then to a flat mirror then through an aspherical corrector lens and one more mirror to the screen. All mirrors are front surface and extremely high reflective.