This is an older set of PVCs, part of a Sonic 2 promotion. It's interesting because it has a sort of out-of-scale Eggman/Robotnik hybrid type figure because they hadn't yet figured out his look for the set. There were 6 figures in the set, so this is only half of it. 

In the image is a Metal Sonic PVC we've seen before, but now you can compare the "Sonic & Knuckles Set" figure to the "Blue Box" figure directly. You can notice small changes like the eye color and stamp on the back of the head.