To complete your collection of trinkets in Thief (opens in new tab), you not only need to find the ones hidden throughout the campaign chapters but also the 27 that are scattered throughout the city hub. To be able to access all of these places, you will need to accept all the jobs from Basso--you don’t need to complete them, just accept all of them at once and you'll have access to every place these items are found in. Otherwise, windows will be boarded up and inaccessible etc.
Jeff McAllister is a freelance journalist who has contributed to GamesRadar+ over the years. You'll typically find his byline associated with deep-dive guides that are designed to help you scoop up collectibles and find hidden treasures in some of the biggest action and RPG games out there. Be sure to give Jeff a thanks in the comments while you're completing all of those tricky Achievements and Trophies.