Collecting gold and silver coins can make investing in precious metals more interesting. As well as the base value of the precious metal in your coin you also have rarity and desirability factors which can raise the bottom line figure.
Certain coins are rarer than others. Apart from their precious metal content, their value depends on their mintages for that year, how many are still in circulation, how popular they are and also their condition.
'Proof' coins are produced to a higher quality are limited in quantity produced and designed for sale to collectors specifically. They generally come in a presentation box and with a certificate.