by Michael Hughes.
Hmm...that's a shame.
You're probably looking at something that customises the "online text" submission plugin then, as your assessment mechanism doesn't really work with file submissions (as they could spend as much time as they want writing the file).
Though off the top of my head I can't think of anything that does this (and a quick look at the Moodle plugins directory https://moodle.org/plugins/browse.php?list=category&id=42 doesn't return any options either).
It may be a question for Tim Hunt as to why the plagiarism plugin stuff for Essay question types hasn't made it in...it would be nice