Here we have two pre-decimal coins on one card - but not really, because it deals with an optical illusion, turning a sixpence into one and six - that being one shilling and sixpence. The trick is to make sure that when you drop the sixpence into the glass of water it lands heads down, then when you look in you see two coins heads up, one large, the shilling, at the bottom of the water, and one small, the "sixpence" on the surface of the water. If the coin dropped tails up you would not get that illusion because the two tails are different.
So lets start with our Hill Reference Book (RB.2) issued in 1942. The catalogue for our set says "Puzzle Series (titled series) size two and three quarter by one and a half inches approximately (except it uses the numbers and fractions). Numbered 1-50. Fronts printed in three colours from halftone blocks with marginal line and white margins. Backs printed black only with descriptions. The title of the series is beside the number - see also "Magical Puzzles"
We have shown a card from that set before so have a look at that, and read that description, by clicking Magical Puzzles.
In my 1950 London Cigarette Card Catalogue it says "Magical Puzzles - see Puzzle Series". And under Puzzle Series it says
Item 68. 50 Puzzle Series
A. Titled "Puzzle Series" (1937) odds 1d. each, sets 6/- each
B. Titled "Magical Puzzles" (1938) odds 6d. each, sets 30/- each
And in our original World Tobacco Issues Index the two sets are listed together under H46-93 and their description is
"Puzzle Series or Magical Puzzles. Sm. 68 x 38 m/m. Nd. (50) see H.636.
A) titled "Puzzle Series" inscribed "Issued by R. & J. Hill".
B) titled "Magical Puzzles". Brand issue inscribed "Issued with Gold Flake Honeydew Cigarettes"
Now I still cannot find it in the handbook under H.636, the London Cigarette Company Handbook for 1950 finishes before that code, and our modern handbook seems to have that number occupied by another set entirely.
If anyone finds it please do let us know where