This is a sub-set of the standard United Kingdom Proof Set of the year, including some of the commemorative coins issued throughout the year, but not the regular circulating denominations.
The 2017 set includes two £5 (crown) commemoratives: King Canute and House of Windsor, plus two commemorative £2 coins: Jane Austen and World War 1 - Aviation; for the first time since the existence of the denomination, these coins were only issued in the year's sets and not released into general circulation. Also included is the Sir Isaac Newton 50 pence.
The coins are struck in Proof FDC grade with frosted finish. The set also contains an oblong Royal Mint medal.