This is a vintage box set by Skor-Mor called Strings N Rings Thinker Series and is Style #179.
There are 4 different puzzles in this set and they WILL make you think! At least one of them will most likely make you wonder if it can be solved, but I've worked them all and they can all be done.
I've had this set for a number of years but don't remember where I got it or if it was new when I did. Box and puzzles are in good though used condition. Some of the rings have lost the brass coloring but other than that it's like a new set.