What do we do when we are unable to determine the Artist or maker of an item? Do we need to report a resale when we are unsure as to whether it is a qualifying resale? 

We suggest using good faith best efforts to do your due diligence, which is probably exactly what you will have done anyway as part of your research into identifying each item you purchase.  We recommend you keep written records of your due diligence in case it is needed in the future, but we will not be auditing your decisions unless independently requested to do so.  If you have any doubts please contact us and we will be happy to help you.