
Leave it up to the buyer of your set if they want it or not.
I personally don't add much value to such certificates. If you follow the link by 999fine, you'll see that they basically only state that they believe their coin or coins are 'collectible', whatever that may mean. My garbage is also collectible according to the trash collector... once a week to be precise.
I have experience with a similar kind of marketing machine in Norway. They sell you coins with a lot of paperwork, but at the end of the day, to real numismatists, they just ruin old (silver) coins by cleaning them. Worst is that they are expensive, too. Anyway, according to their own certificates, they don't necessarily sell (valuable) coins at competitive prices, they sell 'samleglede', or 'the joy of collecting' for overpriced stuff.
