by Chris Morse
“Endgame” (after Canadian coin is found) by Dan Katz and Greg Pliska
Problem:

When you look at the web page for this puzzle, you see 52 round images that all have either an obverse (front) or a reverse (back) of a coin on them. Some of them should be familiar as sides of coins you could find in your pocket today, while others of them are much older. With some research, you can discover that all of them are official minted U.S. coins intended for general circulation (no collector-only coins). If you count, you’ll find that there are exactly 26 obverses and 26 reverses. These 26 obverses are all American coins from the 19th and 20th centuries. The 26 reverses of coins each match uniquely to one of those 26 obverses. In some cases, styles of coins, mint marks and other logic can be used to put these coin sides back together as a pair.

If you click on any of these 52 coins, it flips over and shows you the “back” of the coin, and each “back” has a round image. There are a total of 26 different images, some of which appear more than once. If you observe carefully, on the back of each of the 26 reverse coins, there is one of 26 unique photos. The photos look very British in nature and Googling British alphabet coin will find what you need. Each of these 26 photos corresponds to the UK Royal Mint’s 10 pence alphabet series of coins (https://www.royalmint.com/coinhunt/); specifically, these are photographs of nearly the same exact content shown on each of these engraved coins.

The key step will be ordering those reverses “alphabetically” by the images that are behind them. This is the ordering mechanism for the puzzle. The obverses have these same images behind them (though not a full unique set of 26), once the obverses are matched to the reverses, the backs (letters) of the obverses (read in order of the reverses) read “ROUND MINTAGES DOWN TO MILLION.” Each of the 26 specific American coins here has a mintage somewhere between 1 and 27 million coins minted. If each of these, in the same order you read the previous instruction in, is converted from 1 to 26 into letters, it spells out “BRING HQ ANY REAL CANADIAN COIN.”

After finding and providing a Canadian coin, you are given a printout of this collage:

Within this collage, you can identify the following images, which can all be labeled with names from the series of 10 pence alphabet coins:

• A menu, written in English (English Breakfast)
• Sheet music for the Coldplay song “X Marks the Spot”
• Clione limacina, or “sea angel” found in the waters of the Arctic (Angel of the North)
• Cricket
• Hogs Back T.E.A. (Traditional English Ale)
• Loch Ness (also known as Giant Haystacks)
• Recipe for a Yeoman Warder cocktail

Taking the letters associated with these coin names spells the answer to the puzzle, EXACTLY.

All of the coins have been rendered into black-and-white images in Photoshop; this is to make the copper coins not stand out as much for matching purposes, but more importantly, even all the silver and nickel coins have toned over time, so that each of the pictures could have been matched by the shade of the silver toning, without even needing to know what most of the images were of. This is also why all of the images are displayed/stored as the same size, so the size doesn’t give away the denomination either.

Note: The numbers in the Obverse and Reverse columns in the following table refer to the ordering of the 52 images linearly on the test page (and their files are named 1.jpg to 52.jpg and 1R.jpg to 52R.jpg for the images on the flip side). The 1 through 52 numbers were assigned to the 52 sides of the 26 coins with a random number generator.

 Name of 10 Pence Coin Pence Letter Coin Pairing Letter Behind Obverse Obv. # Rev. # Mintage Letter Mintage Million Coin details Notes Angel of the North A 1 R 22 24 B 2 Peace Dollar - 1926-D Bond . . . James Bond B 2 O 13 49 R 18 Roosevelt Dime 1955-S Cricket C 3 U 28 31 I 9 Barber Quarter 1904 Cannot match with D on Barber Half Double Decker Bus D 4 N 6 26 N 14 Indian Cent 1874 English Breakfast E 5 D 19 34 G 7 Buffalo Nickel 1929-S Fish & Chips F 6 M 5 16 H 8 Liberty Nickel 1912-D Only one with a possible mint mark Greenwich Mean Time G 7 I 27 36 Q 17 Barber Dime 1914 Cannot match with mint mark above wreath Houses of Parliament H 8 N 45 50 A 1 Half Cent 1804 No Crosslet 4 Cannot match the Large Cent Ice Cream I 9 T 52 25 N 14 Mercury Dime 1937-D Jubilee J 10 A 47 46 Y 25 Eisenhower Dollar 1978 King Arthur K 11 G 3 33 R 18 Franklin Half 1960-D Loch Ness L 12 E 14 29 E 5 Liberty Nickel 1883 No Cents Only one without cents Mackintosh M 13 S 44 11 A 1 Standing Liberty Quarter 1917-S Type I No breastplate NHS N 14 D 38 10 L 12 Morgan Dollar 1900-O No CC possible this year Oak Tree O 15 O 32 9 C 3 Large Cent 1803 Post Box P 16 W 23 48 A 1 Twenty Cent Piece 1875-S Queuing Q 17 N 2 20 N 14 Shield Nickel 1866 Rays Must match one with rays Robin R 18 T 21 51 A 1 Morgan Dollar 1891-CC Stonehenge S 19 O 15 18 D 4 Shield Nickel 1873 Open 3 Closed 3 is different Tea T 20 M 1 41 I 9 Washington Quarter 1938 Cannot have a D Union Flag U 21 I 39 30 A 1 Barber Half 1915-D Villages V 22 L 43 35 N 14 Washington Quarter 1944-D World Wide Web W 23 L 12 4 C 3 Nickel 3-Cent Piece 1868 X Marks the Spot X 24 I 40 37 O 15 Liberty Nickel 1887 Cannot have D  or no cents Yeoman Warder Y 25 O 8 42 I 9 Seated Liberty Dime 1875-S Above Wreath Zebra Crossing Z 26 N 7 17 N 14 Lincoln Cent 1927-S