Hello all, I am new to the forum and a relatively new collector and am seeking some advise from some more experienced collectors! My area of interest is proof coins and I have purchased a few proof coin sets. I have just had the 2013 set arrive from the royal mint. However I have noticed a couple of small imperfections on one of the coins, a rusty red/brown mark, about 1mm in diameter. What are these marks? Should I send it back to the royal mint for a replacement? Many thanks for any advise Rob