Hitachi SX - 1981 - US
1964 - Maxell Electric Industrial Co., Ltd. changed its name to Hitachi Maxell, Ltd
In essence Hitachi Cassette Tapes are Maxell re-branded cassette tapes.
In this case SX-C90, a tape manufactured circa 1981, it is fairly safe to assume this tape is none other than a re-branded Chrome Bias Maxell XLII-S.
These are very rare tapes and there are very few to offer.
Note 1: 90 Minutes: Plastic wrappers during this time (late 70's, early 80's) have typically become very brittle and have literally disintegrated into many split pieces, but not these. These have perfectly kept plastic wrapper which makes them even rarer!