Now that I have installed a variant of Linux on my old computer, I could handle the format of the file on this tape.
The label says it is from 1983 and it is in TAR format. This format is still a mainstay on Linux computers. In this case, it is not a problem of software, but of hardware. I wonder if there are still any mag tape readers for this kind of tape. I also wonder if all the magnetized bits have faded into randomness.
If you are wondering who Elsie was, she was my μVax computer in my office at Digital Equipment Corporation.