I got these puzzles recently from Japanese puzzle designer, Mineyuki Oyematsu, or MINE as he known in the puzzling community. MINE runs a website where he sells a range of mechanical puzzles. The site is all in Japanese and the Coin puzzles don't appear to be listed on the site. But you can contact MINE directly via his international mail order link which is in English.
Each of the puzzles have got rather cute names such as "Hard-Boiled Coin", Hole Vacancy Coin and "Remove A! Coin (^^)". There is also a fourth heart-shaped version called "Lucky Sixpence" which I now regret not getting.
The object of each of the coin puzzles is, yes.... to remove the coin. All three puzzles are made of precision laser cut acrylic and the puzzles are made by layers stacked and screwed together. Quality of manufacture is excellent with nicely etched wordings.
In terms of difficulty, Hard-Boiled and Hole Vacancy are not difficult and I solved both quite quickly. Notwithstanding, both puzzles are rather tricky and may throw some puzzlers off for a bit because their mechanisms are well hidden.
However I had some trouble with Remove A! Coin. Took me quite a while to figure out the mechanism and even then, after a few tries, I am still not exactly sure how the puzzle works. Of the three, this last one is the most tricky and difficult. I checked with MINE and he confirmed indeed the puzzle had a few tricks not found in the previous two.
Very nicely made and pocket-able puzzles worth getting, and value for money too; their prices ranging from 1,700Y (US$14) to 2,100Y (US$16).