After my first release (Store Upgrade Parts in Chests), I got into a conversation asking if other items could be included. I had already personally discovered that Microscope Slides were also included, so I decided to broaden my search and look for all items that can only be held by Sims.

Upgrading is simply a state assigned to each item, usually upon placement in the game world. They usually have three possibilities: Not Started, Partial, and Complete.