Thanks for the heads up. I will check the backs tomorrow and update the info. As far as the bolt pattern, i thought the same thing, originally. I measured them though and they came out to 4.5. Which is equivalent to 114.3.
While your looking on the backs, see if the bolt pattern is there as well
eBay Guides - Wheel bolt patterns - Mercedes Benz
below is an excerpt from the above link concerning how to measure
"On a 5 bolt pattern, it is a bit trickier to measure without special tools. Imagine a circle running through the centers of each bolt hole. You would measure from the center of one bolt hole to the imaginary circle that lays between the opposite two bolt holes."
Don't know how you measured, but if you could draw a 112 mm circle accurately on a piece of paper, then cut it out and overlay it on the bolt holes, you might get a better idea.
Scroll down that link and there is a list of Benz and bolt pattern size by year/model, I don't see 114.3 listed there, and I can't imagine AMG wheels made to fit other cars.
Here is another link that shows cars that do have a 5 x 114.3, Mercedes isn't among them...
Wheel Bolt Pattern Cross Reference Database and Conversion Guide: 5X4.5
Also, while you looking on the back, see if you can find a part number, if it's a real Mercedes part number that will solve the mystery.