Hitachi SX - 1981 - US
1964 - Maxell Electric lndustrial Co., Ltd. changed its name to Hitachi Maxell, Ltd
In essence Hitachi Cassette Tapes are Maxell rebranded 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 XL-II-S.
These are very rare tapes and I don't have many to offer.
Note: The plastic wrapper on these tapes are extremely brittle but they all have bits and pieces of the original wrapper. They all have been re-sealed with industry standard 75 gauge shrink film to protect the original wrapper from getting additionally damaged. If your choice is to unwrap them to see them or record them, you will verify the original wrapper has managed to maintain the tape inside untouched, unopened and intact.