Some of you may have seen this picture tube listed on eBay. Well, I'm the one that took a chance on it.
It arrived safe and sound although the box is in rough shape.
The only mark or label on the CRT is a "10X" written in marker.
Anyone know what this tube is ? Perhaps experimental ?
I tried testing it as a 10BP4, but had to drop the bias from -52 to -36 to get the cutoff in the black box. It test very strong and has an excellent life test.