NOS Booster, use or rebuild?

That style booster is expensive rebuilt but not terrible, I bought one that was rebuilt by I believe the same place, top notch. I did this because the used one I put on the car was not working. I didn’t notice because I went from 4 wheel manual drums to power disc/drum and even with the non functional booster I was light years shorter stopping distance compared to the worn out stuff I replaced.

And for clarity, it’s fairly low risk to try an unknown booster on a car. As long as the pushrod still moves in the booster the worst case is you don’t have boost from the booster… it’s not a total brake failure situation. I agree you want to fix it ASAP, but it’s not like it’s going to cause you to drive off a cliff, that’s caused by rapid loss of brake fluid.