So this is probably another one of my fringe case, one off type designs, but there it is...
I have this little brass caliper that I found in my tool drawer. To keep it from getting damaged, I decided that it needed a case. Unless you have this exact caliper (and you know who you are!), you probably don't need this as it is, but the tray could easily be modified to fit what ever object you'd like to use it for.
This is designed so that the tray snaps into place once inserted into the case via two small bumps at the bottom. It takes a little bit of force to push it in and to pull it back out, but once it's in, it's not going to just slide out. I added a finger hole through the tray so that you can easily push the caliper out.
Since I've been playing around with FreeCAD, I decided that this would be a good test of my abilities (or lack there off). Never one to start off with the easy projects first, I began. Coming from almost a decade of SketchUp experience, I am used to importing an image in to the program and tracing it out, then extruding that shape. If that can be done with FreeCAD, I missed it, so I had to take measurements of everything and manually draw the caliper shape into Sketcher. Straight lines I'm good with... no so much arcs. The arcs do not line up perfectly, but they are close enough to serve their purpose here.
If anyone wants the source file, I'll be happy to upload that for you, but I warn you now that, as a complete newbie to FreeCAD, my workflow and organizational skills with this program will probably leave you scratching your head wondering "what in the hell?"