The C Class one doesn't look like a sticker either - I had a scratch and it didn't do anything - I think its etched in - for future when you buy a C Class second-hand you'll know if it has a replacement screen (Not sure what that tells you though)
My C Class has the signature. It’s the same black material used to black out parts of the window so definitely not a sticker. Last week I had a brand new A Class loan car it’s windscreen was just signed Mercedes.