You already know the trick locks, the trick bolts. Now let me explain a little bit about the trick keys.
I don't see this kind of puzzles a lot and the only ones I know are designed and crafted by Rocky Chiaro using brass (like for all his puzzles). The goal is obviously to free the ring.
The price is definitely not cheap but the quality is very good and it's handmade. This has a price!
It puzzled me for few minutes, so I have to admit that it's not a difficult puzzle at all. I remember it was ranked with a high difficulty on Rocky's website but he has deleted the difficulty.
I like the mechanism and the name of the puzzle, always funny names for his puzzles!
So you should buy it if you have no trick keys in your collection or if you like metal puzzles. I would have liked a bit more steps and a bit more difficult. But well, it must be difficult to implement a lot of steps in small puzzles like trick keys...