In WO-Q, (or DC-I) when I click on archived work orders and enter a archived work order number I get the following message:
This work order number already exists in the Archive WO files, please enter a different work order number.  Click Okay, then:
The valid check for this field returned false, please re-enter.
 
If I use the look-up I can pick the same work order and it will come up just fine-- minor inconvenience but thought you would like to know.