Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5859209.

I only have one NES manual (Zelda) but I wanted to display it next to the cartridge. This is just a simple frame, a stand to slide the frame into and a back plate help keep the manual inside.

The manual I have is inside a protective sleeve from an eBay seller 'RetroProtection', that adds a little extra length and width, so I designed this frame to accommodate the manual inside this sleeve.

I'd recommend doing the same for better protection rather than putting a manual inside with nothing. But if you do, you will need to scale down at least the vertical direction a few mm and do the same for the back plate.