MSI/Plessey supports digits as its character set. It's more common to use it with one or two check digits as in below.
This is MSI/Plessey with a modulo 10 check digit.
This is MSI/Plessey with two modulo 10 check digits.
This is MSI/Plessey with a modulo 11 check digit.
This is MSI/Plessey with a modulo 11 check digit followed by a modulo 10 check digit.