Padlock 01 - Zann's Last Masterpiece Mystery Cache

After 4 active years we’re calling time on this geo-art.  We’re giving everyone until 1st April 2020 to solve / find these caches, after which time we’ll be archiving this series

This is one of a series of puzzle caches which we have decided to put out.  Remember to keep an eye out for the information you will need to use to solve the final cache in the series.  Enjoy.

When they broke down the door to that attic room on the Rue d’Auseil all they found was this...

But what does it mean?

You can validate your puzzle solution with certitude.

Alert: You are about to download a file that contains further details needed to find this geocache. As the cache owner, I represent that this file is safe to download although it has not been checked by Groundspeak or by the reviewer for possible malicious content. Download this file at your own risk.