PCGS & NGC are the main two impartial Numismatic Grading Services in the world and is a guarantee that the coin is genuine and has been graded accurately and professionally.
The sonically sealed solid plastic slab is individually numbered so that the details of the coin(s) can be verified on a central database, and is also tamperproof.
In addition, the coin is protected from handling and keeps the coin(s) condition and finish long term if looked after which can be detrimental to the value once sold.

Outside the UK? Not a problem I use eBay global shipping, look at the costs available from your end. All items ship from the UK.