What is the exact requirement for a password to be considered a valid encrypted secret

I need to be a little vague to avoid test comp, but there is one question I keep thinking back on even days after my test that is bugging me.

When you enter an enable secret command and specify an encryption level, let's say 5, and enter a password what exactly is the criteria that it's looking for to determine that what you've entered is a hashed value and not plain text?

For instance, enable secret 5 C1$C0T3$T$aRE$TuP1D Is clearly in plain text but could it be messed up enough that the router thinks it's hashed and be accepted? What exactly is it looking for to make that distinction? I'm upset that Cisco is even making me consider this little nuance, but I can't find an answer anywhere.