Hello it seems unbelievable. I bought a set of a 45-105 double ball end strings from a well known brand. I placed them yesterday and the D string Looked different : upon close inspection,  the ball end is made of brass instead of chromed metal, the wire is darker and, tadam, there are wear marks at frets intervals ...  incredible...  I have contacted the online shop and I am waiting for an answer. I wonder how they will handle this case. My word against their word...  i don’t