1970 UK Proof Mint Set

Thanks, jbuck! And, now that I know what country this actually from, I was able to do a little research and discovered that it's the last "pre-decimal" set that was made by The Royal Mint. The full name of the set is "THE COINAGE OF THE U.K. OF GREAT BRITAIN & NORTHERN IRELAND" and it contains a Florin, a Half Crown, an English Shilling, a Six Pence, a Scottish Shilling, a Threepence, a Penny and a Half Penny.

English and Scottish shillings.

Fair enough, but why this denomination and not the others, was it because of some historical significance?

The sets with perfect pack and info can be bought retail for about £20. Although I have amassed over half a doz sets bought for less than £10.
A die crack would probably be a negative.Bad toning on the copper is also not good. Hence you see many single coins from this set on ebay...A hearty meal at MacDonald's (if such a thing exists) is your answer.