'Proof’ is not a grade; it is the method by which the coin is manufactured. Proof coin manufacturing has been in vogue since the 19th century. Initially, proof coins were struck for checking the dies and for archival purposes.  But now they are struck especially for coin collectors. Proof coin collecting has now reached a point where collectors try collecting the proof sets with all denominations for every year starting from 1936. Sometimes collectors get a particular year set to make wonderful presents for any milestones achieved in the family like birth, graduation, landing a job and so on.