Originally, 7- and 9-track data tapes only had human readable labels on them (i.e. as far as the operating system was concerned they were unlabeled).
This metadata allowed the operating system to quickly recognize a volume and assign it to the program that wanted to use it.
Some computer systems used similar labels on other serial media, for example punched card decks and sometimes line printer output.
The Burroughs MCP running on the B5000 was one of the earliest systems to automatically read tape labels.
When designed in 1961 it used a proprietary format coded in BCD (strictly, Burroughs Interchange Code or BIC), but was later able to read standard 7-track ANSI (then styled USASI) labels.