IEC Type II tapes are intended for recording using high (150% of normal) bias and replay with the 70μs time constant. All generations of Type II reference tapes, including the 1971 DIN reference that pre-dated the IEC standard, were manufactured by BASF. Type II has been historically known as chromium dioxide tape or simply chrome tape, but in reality most Type II cassette tapes do not contain chromium. The "pseudochromes" (including almost all Type IIs made by the Big Three Japanese makers — Maxell, Sony and TDK) are actually ferricobalt formulations optimized for Type II recording and playback settings. A true chrome tape may have a distinctive old crayon smell, more specifically, any oil or wax chalks that have chrome dioxide pigments in them like chrome yellow, which is missing in "pseudochromes". Both kinds of Type II tapes have, on average, lower high-frequency MOL and SOL, and higher signal-to-noise ratio than quality Type I tapes. This is caused by the midrange and treble pre-emphasis applied during recording to match the 70μs equalization at playback.