Parts.

I acquired the following parts:

One N20 6VDC 30RPM gear motor.
One 3.7V 160mAh lithium polymer battery with suitable charger and mating connector with wires.
One 16" length of 2mm diameter metallic music wire (ferrous).
One 6mm diameter by 2.5mm thick neodymium magnet.
Nine 15mm diameter by 2.75mm thick neodymium magnets.
I 3D printed the following parts at .15mm layer height, 20% infill with no supports:

One "Base.stl".
One "Bottom.stl
One "Heart, Inner, Cover, I Love You.3mf" (dual extrusion).
One "Heart, Inner.stl".
One "Heart, Outer.stl".
One "Holder, Magnets.stl".
One "Top.stl".
I have also include the parts "Heart, Inner, Cover, I Love You Letters.stl" and "Heart, Inner, Cover, I Love You.stl" if you wish to print the cover on a single extrusion printer then glue the letters to the cover, and I've also included the part "Heart, Inner, Cover.stl" if you wish a blank cover to which you could leave blank, glue photos, apply stickers, or simply draw on.

This is a medium precision 3D print and assembly model. Prior to assembly, test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.

Assembly.

To assemble the model, I performed the following steps:

Pressed one of the larger magnets into the magnet pocket in "Heart, Inner.stl".
Cut a 22mm length of music wire, pointed the ends using a hand held motor tool, then pressed it into the lower hole in the inner heart assembly.
Cut an 18mm length of music wire, pointed the ends using a hand held motor tool, then pressed it into the upper hole in the heart assembly.
Pressed "Heart, Inner, Cover, I Love You.3mf" onto the front of the heart assembly.
Pressed eight of the larger magnets into "Holder, Magnets.stl".
Pressed the magnet holder onto the shaft of the gear motor.
Soldered the mating connector wires to the gear motor.
Inserted the mating connector wires into the motor hole in "Base.stl", then pressed the motor into the base until the magnet holder was 1mm below the top rim of the base.
Pressed "Top.stl" onto the top of the base assembly.
Pressed the smaller magnet into the magnet pocket in "Heart, Outer.stl".
Pressed the outer heart into the base assembly outer heart pockets.
Plugged the lithium polymer battery connector into the motor mating connector, made certain the magnet mount rotated with ease, then carefully positioned the battery and wires into the base assembly.
Pressed "Bottom.stl" onto the base assembly.
Positioned the inner heart assembly lower pin into the lower hole of the outer heart, the attached the upper pin to the outer heart magnet.
With assembly complete and the motor running, the inner heart began rotating!

And that is how I 3D printed and assembled "For My Valentine, 2023.".

I hope you enjoyed it!