Was browsing Elasticsearch issues on github and came across this comment stating that:
Multi-token string fields are not sortable by Elasticsearch in any predictable way.
For reference we are talking here about a string timestamp in the form "14/05/08-13:41:23".
From the context, I would assume that any non alphanumerical string (with other chars than [A-Za-z0-9]) would be a multi-token String?