London Vintage HiFi Market - Calibration Cassette Speed Playback Professional Test Tape 3000 Hz (3 kHz) frequency Type II Clear Chrome for Stereo Cassette Deck, Walkman, Answering Machine, Boombox, Cassette Player -
Marantz Calibration Tape | Stereo2Go forums
WLA SC1 3kHz + 3.15kHz Speed + Wow / Flutter Calibration Test Tone Cassette | Reverb España