A ring holder with a secret hiding place for a more important ring.

The "display" ring can be a decoy.

Should be press fit. If it isn't, you'll need to adjust the flow rate on one of the pieces by a tiny amount. Try to avoid scaling either piece; make the fit tighter or looser by extruding a bit more or less (try numbers around 1% - 3%, or between 0.97 to 1.03).