SIXBIT
From Computer History Wiki
SIXBIT is a predecessor encoding system to ASCII; it too supported encoding various glyphs (written forms such as letters, numbers, etc) in 6 bits (hence the name); it only supported upper-case characters, however. SIXBIT contains the characters with ASCII codes from 32 to 95; to get the SIXBIT code for one of these characters, simply subtract 32 from the ASCII code.
It allowed 6 characters to be carried in the then-common 36-bit words common on many computers; with 18-bit and 12-bit computers then being common also, it had wide utility.