"Proper case" (or Title Case) typically capitalizes the first letter of each word and acts on text, not alphanumeric codes.
(If it is a model number, part number, or serial code, it is best written in all-caps, as numbers are considered neutral and letters in codes are usually capitalized for clarity). 68539x
Based on standard capitalization rules, the "proper text" formatting for depends on its context, generally resulting in: "Proper case" (or Title Case) typically capitalizes the