hexdump(1) on macOS
The text 91821e7a5a1b, as Mac OS X 10.5.8, Mac OS X 10.5.7, Mac OS X 10.5.6, Mac OS X 10.5.5, Mac OS X 10.5.4, Mac OS X 10.5.3, Mac OS X 10.5.2, Mac OS X 10.5.1, Mac OS X 10.5 shipped it.
ASCII, decimal, hexadecimal, octal dump
Flags it lists
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-C -
-b -
-c -
-d -
-e -
-f -
-n -
-o -
-s -
-v -
-x