BMW vins are indeed engraved with stars at the front and rear of the frame.
A frame was replaced in the dealership i work at last year and the person who stamped the new frame made a bodgery of it. It naturally came back to us for us to sort out. I ended up having to grind the frame back, fortunatley the vin plate was very thick and stuck out a bit from the frame itself so i had a bit of metal to work with. You should have seen my practice piece of steel, i swear by the end of it i could see the vin in my sleep lol. The best bit was doing the stars at the start and finish, you cannot get them as a stamp so i had to end up free hand scribing it into the vin plate. All came out well in the end i think i spent about 6 hours on it in total getting it right but still doenst look anything like a factory stamped frame as BMW engrave them in and the letters are twice as tall. We tried looking for someone that would engrave it but everyone we tried basically said the frame would be to big for them to work with, all the engravers we found were jewlers, trophy scribers etc. What really annoyed me was when i rang bmw about getting a suitable stamping kit they basically said any one would do, we already had a kit, yet they expect it to be done correctly. I dont see how we can do this correctly if they dont supply us with a kit with a jig etc. We had to write the customer a letter stating that we had replaced the frame for warranty and that all the details are on our system if it needs questioning.