This Achievement requires you to find 2 masks in the "Stealing XMAS" heist. Both masks have multiple locations where they may spawn.

1. At a bench next to the giant christmas tree



2. In a trash bin left of the shoes store



3. On the roof

1. At the stairs next to the jewelry store



2. At the wine store



3. At the crates in a room next to the tech store

The Masks will spawn at every difficulty. I hope this guide helped you!