I've lost track of the photo, but I've posted it several times.
I started by keeping the COAs in a photo album. You had to find just the right one because some of the Certificates are a smidgeon larger than 4x6.
I believe the print I found was a "Pioneer" that held 2 COA side-by-side in an 'open' way so that the histories could be read when they were inside the album.
Now, they are stuffed in a box somewhere.