Singer made a series of retail systems which were taken over by ICL and rebranded.
The ICL System 10 used 6-bit bytes for decimal and character data.
The ICL System 25 used 8-bit bytes, which were used for full ASCII text, and in arithmetic operations as packed decimal (two 4-bit nibbles holding 0x00 to 0x09).
Singer were fairly adventurous. They made sewing ...
Really early computers like the Mark I and ENIAC didn't have enough memory to attempt to handle text; also the use-case was mostly calculations.
A number of decimal IBM computers used characters (with 5 or 6 usable bits) as the basic unit, and decimal digits were just a special usage of those characters:
The IBM 1401 computer, and its compatible successors ...