I am not sure if Skeletons are really considered monsters. They are certainly in the realm of things we consider to be scary and Monsters are considered scary, so, if A=C and B=C, then A also =B.
I recently found these in a discount surplus store in Winnipeg kinda tucked out of plain sight on a higher shelf. It was the only one there. Generally they would be selling the keychains individually so I was happy that they were all there and I could get the whole lot. The display card is what I was really after but is certainly nicer with all the keychains on it. I don't think it's a particularly older item and I'm not sure why one of them is green. Now to find my old skeleton keys.