The Reference is an unresponsive yoyo, designed around Fluid Printdynamics' 3d printed yoyo spacer kit. It was created by Luftwerk's Jeffery Pang to facilitate 3d printed yoyo iteration in 2014. Kits are still available for purchase, and I highly recommend starting there. 

The design has cavities to set the weight out towards the rims, while prioritizing a clean outer look. It minimizes overhangs, and gets a nice fileted edge without compromising the first layer. Adding a color change in the first few layers of the print will give a great contrasted edge to it.

If you can't get ahold of the spacer kit, I've included a printable version that doesn't need the kit, instead seating the bearing against plastic. You'll get more vibe without the brass spacers, but it's servicable. Here is the hardware list in that case:

1x 4mmx0.7 20mm set screw

2x 4mmx0.7 hex nuts

A type C yoyo bearing

2x 19mm silicone yoyo brake pads (the throw should accommodate most designs)

I recommend printing in PLA for consistency, at 100% infill. I printed on Inland Tough PLA in black, and marble. Should not need supports or a brim.