I picked up an old tube tester from a friend of my Dad. Nothing fancy, it's from a company called Accurate Instruments out of NY. It tests for shorts and emissions. Anyway, I have no idea how to read the meter. I tested a bunch of tubes that were supposedly NOS or lightly used. The meter has a scale of 0-100 with bad from 0-40, ? from 40-50, and good from 50-100. All the tubes I tested were between 50-70. Shouldn't a NOS test close to 100? Either I'm not reading it right, I got screwed from the dealers I bought the tubes, or the tester needs to be calibrated. Any ideas?