MIL-STD-6016 requires at least 1, and possibly another different 5-bit encoding. These take 22 alpha characters (a-z without I and O, and without two other letters, Tbd), and combines them with 0-9. One(1) and "I" are considered the same character, and zero("0") and "O" are considered the same.
The mappings of character code points to characters may be different - e.g., one may have digits 0-9 in values 0-9, followed by the alpha characters. Others may have it the other way round.
These encodings would be X-DFDL-ASCII-5-Bit-.... something or other. They would be bit aligned, and use bit-order least significant bit first.
Since we will have 7, 6, and 5 bit encodings it is natural to add 4 (hexadecimal), and 3 (octal), and 1 (binary). Which might be very convenient for some purposes. There are formats where, for example a number is stored as 5 octal digits. If we can use octal as a character set encoding for 3-bit-wide character codes, then this becomes a textStandard number in textStandardBase of 8.