Calibration Tapes

Hello everyone. Just curious which calibration tapes you all are using. I bought a couple of sets from eBay from two different sellers, one was a former Nakamichi technician and the other seems to rule eBay when it comes to selling calibration tapes. Both claim that their tapes are recorded from reference calibrated decks. The two brands differ in accuracy, I have no idea which is accurate, if either. I noticed it recently when I serviced and calibrated my main cassette deck [Nakamichi CR-2a] with the latest calibration tape that I had bought. Recorded a vinyl onto cassette and it sounded fabulous. I played that cassette tape on a serviced Walkman and it sounded very good, but not superb. I hooked the scope up to the Walkman that I had calibrated from my original calibration tape but used the new calibration tape this time. It was then that I noticed that the azimuth was off. I checked other Walkmans in my collection that I restored from the past year or so, they too were off.

Seems there is no consistency with these home brew calibration tapes. Got frustrated and ordered a full set from Germany, from Hans Roth. I suppose if I just picked one brand and calibrated all my devices with it, it would be fine. But, I'd like to know that I was calibrating to a recognized and verified standard. What are you folks using for calibration tapes? Please don't tell me the 40 year old TEAC calibration tapes that sell for an arm and leg. Cheers! Norm