So I recently picked up this Copic Swatch Book. I do have the free printable A4 chart from Copic, but I thought this would be a really handy size to take with you if buying your markers from a physical store, not online. You can take it along and easily check what markers you have and what you might want to purchase.
This book is made by Copic and is printed on X-Press It Blending Card. There are instructions on the first page stating that for consistent results, use the medium broad nib and make one even stroke in associated box.I currently have 63 Copic markers, which I have swatched in the video above, but if you would like a closer look, here are pictures of the individual pages for you.