What company did you send the wheel off to? When I had my last Golf, I sent the Monza IIs off to Pristine and they said that to keep time scales to a minimum they try and keep a stock of alloys in so they can just recieve the damaged ones, inspect them and if all is okay they will return the already refurbished stock wheels. This was for a full set mind you and they didn't have enough stock of them when I sent mine away about 2 years or so ago so actually refurbed my supplied wheels.
Maybe this is what the refurbishers did to you and inadvertantly sent you a different spec wheel. Have you spoken to them about it?
Also the reason the finish on the paint is different on the Ronal could be that it has already been refurbished and the standard isn't quite as high as an OE factory finish.
I'm sure if you speak to them they could explain.
Also, just for fellow anoraks out there, Ronal make the Monza alloys on the Polo GTI too. I thank you