These are nice little hermetically-sealed metal film resistors, and have dates from 1973-74. Found these guys in a $1 grab bag from the local electronics shop. A few of them came in the tubes toward the back, and the rest were by themselves. The writing on the tubes sure made it easy to identify them!
Here’s a PDF datasheet about them from Vishay. While that helps with the specification, Vishay has more notes about the construction of them.
I must admit, even though I had come across these while disassembling stuff, I never paid any attention to them. There’s another sheet, from which the above diagram was copied, about the technology. My favorite line:
“Use in hostile environments. Corrosive environments and
atmospheres have no effect on the resistor. Each resistor
is tested with an external force of 3000 PSI. Excellent for
chemical and other process environments as well as
saltwater, high temperatures and space.“
Space. Yessir, space. Just think, their siblings (re-sisters? eh?) could likely be floating around the planet right now, circling around on an old satellite. Now that line of thinking may be a little extravagant, but it’s an interesting structure.They are still made, more often replacing the glass structure with aluminum, brass, and other metals.
And because every extreme component needs an awesome demo, here’s a video of Vishay pressure-cooking one of their hermetically-sealed resistors: