betanumeric

Consisting of, or limited to, the set of lowercase alphanumeric characters (letters and/or numbers) minus vowels and the letter 'l' (ell). Specifically, that set consists of: bcdfghjkmnpqrstvwxz0123456789.

To create durable, opaque, transcription-safe identifier strings, it helps to limit them to betanumeric characters and to add an NCDA check digit at the end.