You want the order number to be visually distinguishable from the other information and accessible to an international audience (many restaurants, even in Engli

You want the order number to be visually distinguishable from the other information and accessible to an international audience (many restaurants, even in English-speaking countries, are run by non-native speakers and may even cater to non-English-speaking customers!). This rules out using English words for your order numbers. The post suggests using all the letters in the alphabet, but then you run into the problem where once in a while someone will wind up with order #F*CK and complain. So you have to add logic to avoid naughty words, but then you get #FOU in France and realize you need to localize your naughty word list. Or, you could stick with numerals, which everyone understands and which everyone is familiar with (and which are obviously order numbers!). Extending to hex is already a bit of a stretch, but at least there's not that many naughty words using only hex digits.