Compact Cassette tape types and formulations - Wikipedia
Amazon.com: Sleeve City ATR Magnetics C-60 Ferric Cassette (Single Tape) : Home & Kitchen
ATR Magnetics Master Cassette - Normal Bias Type I - Ferric 60 min — ATR Magnetics
FERRITE LINE FERRIC 60 TYPE I BLANK CASSETTE TAPE (1) (SEALED) | eBay
Old Transparent Plastic Audio Cassette With Brown (ferric Oxide) Tape For Domestic Magnetic-tape Reader.Similar Cassette Were In Use In 1960-1990. Sometimes It Was Used As An Alternative Computer Storage Medium Like Floppy