A 30mm hex base for Gloomhaven monster cards with a 2nd slot for the modifier bits. The center rotates and has a pointer to the outer dial which is numbered 1-18 to keep track of monster HP. 

Holder and Dial print separately and come apart easily, but the cardboard insert stops the dial lifting off when in use. 

Updated file GH-PrintInPlace prints as one piece and does not come apart without breaking. It has pretty low tolerance (~0.2mm) as I wanted it to click into place over the numbers. If it is sticking when it comes off the printer, I suggest using something like a bottle top to support the ring and tapping the center part close to the the ring, very, very lightly with a small hammer from top and bottom. Trying to twist the parts loose might break it, depending on your wall thickness etc.