The people I bought my house from had wallpapered almost every single room. It was a nightmare to remove. I still cringe every time I see wallpaper because of that! I don't think the 8903B would benefit from calibration. It exceeded the performance test for distortion when I checked it out. And for what we do, there's really not much that you'd need to have calibrated. Maybe a counter or signal generator for FM work. I went way overboard for timing. I had picked up a distribution amplifier in a lot of test equipment, and bought a GPS disciplined oscillator from the auction site. I use it to clock all my time based equipment that has an input for external clocking. My AM/FM generator doesn't, but my counter (which does have an external clock in) shows it's good out to 4 decimal places. Not good enough in the metrology world but more than good enough for an FM tuner. One of those things that I just did because I could. Although admittedly it does come in handy for the occasions when I repair test equipment.